Bird Feeder

Abstract

A bird feeder 1 comprises a feed portion 2 configured to receive a feed mixture 5 and an attachment means 3 for attaching the bird feeder to an external structure. The bird feeder 1 is a unitary membe

Description

The present invention relates to a bird feeder. In particular, a bird feeder of the type used to retain feed mixtures for the feeding of wild birds. Background Use of bird feeders to feed wild birds, particularly during cold periods and / or spells of inclement weather, is widely practised around the world. Many bird feeders comprise a container which accommodates an assorted seed mixture or other loose feed. The feed is allowed to fall under the force of gravity towards a hole, perch or tray where a bird can access the feed. While such feeders can be easily re-filled and re-used, they can become blocked so that food will not be dispensed, and are not suitable for dispensing higher-energy foods such as suet-seed cake which wild birds often prefer during certain periods, for example in winter. Another popular type of bird feeder is one having a container which retains a high energy solid feed. The container has an aperture through which birds can access the feed. Such bird feeders are often made from natural products such as a coconut shells. Natural products are advantageous because they are biodegradable and therefore have a low environmental impact when disposed of at the end of their useful life. A feed mixture in a liquid or semi-liquid state can be poured into the shell through the aperture. The feed mixture is then allowed to harden or set before any excess feed which protrudes out of the shell through the aperture is removed. While coconut bird feeders are biodegradable, can dispense high-energy food and do not suffer blockages, coconut shells are natural products having a non-uniform size and shape. This complicates the manufacturing process as well as making the finished products difficult to package within delivery and shipment containers. For example, each coconut will have a slightly different size and shape and therefore will accommodate more or less feed than the average. Using a standard volume of feed in each shell will result in some products looking unfilled, while using a bespoke amount of filling in each shell complicates the manufacturing process. The variation in shape also makes it difficult to securely hold shells while they are being filled and while the feed mixture sets. This means that coconut bird feeders are often filled by hand and the amount of filling in each shell must be varied from product to product. Furthermore, raw natural products such as coconut shells cannot be grown everywhere in the world. While many of the world’s leading coconut producers are located in Southeast Asia and South America, many users of coconut bird feeders are not. Coconut bird feeders ultimately rely on the use of petrochemicals in the transport of raw and / or filled coconut shells over large distances. There exists a need for a more environmentally-friendly way to produce bird feeders. Objects of the invention It is an object of the invention to provide an improved bird feeder. In particular, it is an object of the invention to provide a bird feeder that can more easily be manufactured. It is a further object of the invention to provide a bird feeder that can be uniformly manufactured. It is a further object of the invention to provide a bird feeder that has a lower environmental impact. It is a further object of the invention to provide a bird feeder that can be easily disposed of. It is a further object of the invention to provide a bird feeder which uses locally-available raw materials. It is a further object of the invention to provide a bird feeder that can retain a solid or fat-based bird feed. It is a further object of the invention to provide a bird feed that simplifies the manufacture of bird feeders. It is a further object of the invention to provide a bird feed that can provide nutritional value to wild birds. It is a further object of the invention to provide a bird feed that has an optimal viscosity for an automated manufacturing process. It is a further object of the invention to provide a bird feed that can be securely retained within a bird feeder. Summary of the invention According to the invention there is provided a bird feeder according to the independent claims. Advantageously, the bird feeder being a unitary member removes the need to produce and combine multiple separate parts during manufacture. Advantageously, use of a biodegradable material means that the bird feeder is compostable and therefore can be disposed of in an environmentally-friendly way after use. Optionally the bird feeder has a uniform shape. Optionally the bird feeder is unitary. Advantageously, the bird feeder being of unitary construction removes the need to produce and combine multiple separate parts during manufacture. Optionally the bird feeder is a unitary member. Optionally the bird feeder is a unitary member comprising a feed portion and an attachment means. Optionally the feed portion is attached to the attachment means. Optionally the feed portion and the attachment means are unitary. Optionally the feed portion and the attachment means are made from a single piece. Optionally the feed portion is integrally formed with the attachment means. Optionally the feed portion and the attachment means are made from the same material. Optionally the feed portion and the attachment means are made from a single material. Optionally the bird feeder is injection moulded. Optionally the bird feeder comprises injection moulding lines. Optionally the bird feeder is 3D printed. Optionally the bird feeder comprises a biodegradable material. Advantageously, use of a biodegradable material means that the bird feeder is compostable. Optionally the bird feeder comprises a 100% biodegradable material. Optionally the bird feeder comprises a plant-based material. Optionally the bird feeder comprises a 100% plant-based material. Optionally the bird feeder is formed from a biodegradable material. Optionally the biodegradable material is a composite material. Optionally the biodegradable material comprises a biodegradable polymer. Optionally the biodegradable material comprises up to 50% by weight of a biodegradable polymer. Optionally the biodegradable material comprises a natural biodegradable polymer. Optionally the biodegradable material comprises a biodegradable polymer made from sugar. Optionally the biodegradable material comprises plant waste Optionally the biodegradable material comprises at least 30% by weight of plant waste. Optionally the plant waste comprises agricultural plant waste and / or cereal waste. Optionally the biodegradable material comprises a filler or additive. Advantageously, the filler or additive can provide additional strength to the material when used in the bird feeder. Optionally the biodegradable material comprises up to 25% by weight of filler or additive. Optionally the filler or additive comprises natural starch and / or a calcium-based material. Optionally the calcium-based material is calcium carbonate. Optionally the biodegradable material comprises food waste. Advantageously, the incorporation of food waste into the bird feeder reduces the amount of biodegradable polymer required in the manufacture of the bird feeder. Optionally the biodegradable material comprises at least 1% by weight of food waste. Optionally the biodegradable material comprises up to 6% by weight of food waste. Optionally the biodegradable material comprises from 1% to 6% by weight of food waste. Optionally the food waste comprises coffee grounds. Optionally the biodegradable material comprises coffee grounds. Optionally the biodegradable material comprises at least 1% by weight of coffee grounds. Optionally the biodegradable material comprises up to 6% by weight of coffee grounds. Optionally the biodegradable material comprises from 1% to 6% by weight of coffee grounds. Optionally the biodegradable material is configured to be injection moulded. Optionally the bird feeder comprises a feed portion. Optionally the feed portion is configured to receive a feed mixture. Optionally the feed portion is configured to receive a suet-cake feed mixture. Optionally the feed portion comprises the biodegradable material. Optionally the feed portion has an elliptical or substantially elliptical cross section. Optionally the feed portion has a circular or substantially circular cross section. Optionally the feed portion is hemispherical or substantially hemispherical. Optionally the feed portion comprises a hemispherical or substantially hemispherical outer surface. Optionally the feed portion comprises a hemispherical or substantially hemispherical cavity. Optionally the feed portion comprises an opening or aperture. Optionally the feed portion comprises a curved, elliptical, circular or substantially circular opening or aperture. Optionally the aperture comprises a curved, elliptical, circular or substantially circular peripheral portion. Optionally the plane of the aperture is flat or substantially flat. Optionally the aperture is configured to allow the feed portion to be filled with bird feed. Optionally the bird feeder is at least partially filled with a feed mixture. Optionally bird feed is able to pass through the aperture. Advantageously, the aperture being adapted to allow bird feed to pass there through means that the feed portion can be filled with bird feed via the aperture and, in use, wild birds can access feed in the feed portion via the aperture. Optionally the feed portion comprises a stabilising means. Advantageously, the stabilising means allows the bird feeder to rest on a surface in a stable manner, for example without rolling. Further advantageously the stabilising means allows the bird feeder to remain at rest during filling of the bird feeder with bird feed. Optionally the stabilising means are configured to prevent rolling of the bird feeder. Optionally the stabilising means comprises a flat portion. Optionally the feed portion comprises a flat portion. Optionally the opening or aperture is opposite the flat portion. Optionally the opening or aperture is on an opposite side of the feed portion to the flat portion. Optionally the stabilising means comprises a flat portion located on an outer surface of the feed portion, and wherein the stabilising means is located on an opposite side of the feed portion to the opening or aperture. Optionally the flat portion is a flat surface or substantially flat surface. Optionally the flat portion is a flat surface located on the outer surface of the feed portion. Optionally the feed portion is configured to retain a feed mixture. The feed portion comprises retaining means. Advantageously, the retaining means ensure that the feed mixture does not move and / or fall out of the bird feeder during use. The feed portion comprises retaining means for retaining the feed mixture in the feed portion. Optionally the retaining means are configured for preventing movement of the feed mixture in the feed portion, in use. The retaining means is located on an inner surface of the feed portion. Optionally the retaining means comprises a keying surface. The retaining means comprises one or more protrusions or fins. The retaining means extend away from an inner surface of the feed portion. Optionally the retaining means extend towards the opening or aperture. Optionally the one or more protrusions comprise one or more cylindrical protrusions or substantially cylindrical protrusions. Optionally the one or more protrusions comprise a plurality of cylindrical protrusions or substantially cylindrical protrusions extending from an inner surface of the feed portion. Optionally the retaining means comprises a plurality of fins extending from an inner surface of the feed portion. Optionally the retaining means comprises a high friction surface. Optionally the inner surface of the feed portion comprises a high friction surface. Optionally the inner surface of the feed portion comprises a featured surface, such as a dimpled or patterned surface. Optionally the bird feeder comprises an attachment means. Optionally the bird feeder comprises an attachment means for attaching the bird feeder to an external structure. Optionally the bird feeder comprises an attachment means for attaching the bird feeder to multiple external structures. Optionally the external structure is a tree or a part thereof, or a branch, hook, nail or post. Optionally the external structure is a loop, ring, string or rope. Optionally the external structure is another bird feeder. Optionally the attachment means comprises the biodegradable material. Optionally the attachment means defines an aperture, hook or opening. Optionally the attachment means defines an aperture, hook or opening for receiving a fixing means. Optionally the attachment means defines an aperture, hook or opening for receiving and / or attaching the bird feeder to an external structure. Optionally the attachment means defines an aperture, hook or opening for receiving an external structure, such as a tree or a part thereof, or a branch, hook, nail or post. Optionally the attachment means defines an aperture, hook or opening for receiving an external structure, such as a loop, ring, string or rope. Optionally the attachment means is an elongate member having opposing end portions Optionally the attachment means is connected to the feed portion at each end portion thereof. Optionally each end portion of the attachment means is connected to the feed portion. Optionally the attachment means is curved. Optionally the attachment means comprises a central curved portion. Optionally the attachment means is connected to the feed portion. Optionally the attachment means is connected to the feed portion at a peripheral edge of the feed portion. Optionally the attachment means is connected to the feed portion at a peripheral edge of the opening or aperture. Optionally the attachment means comprises at least one recess. Optionally the attachment means comprises at least one projection. Optionally the attachment means comprises a recess and a projection. Optionally the recess and projection are located on a single face of the attachment means. Optionally the attachment means comprises a flat face. Optionally the flat face of attachment means is parallel or substantially parallel to the plane of the opening or aperture of the feed portion. Optionally the recess and projection are located on a single flat face of the attachment means. Optionally the recess has a complimentary shape to the projection. Optionally the recess is shaped such that it is configured to fit inside the projection. Optionally the recess is shaped such that it is configured to fit inside the projection in a push-fit or tight manner. Optionally the recess is shaped such that it is configured to receive a projection of a further similar bird feeder in a push-fit connection. According to another aspect of the invention there is provided a system comprising a plurality of bird feeders, wherein the plurality of bird feeders are attached to one another. Advantageously, the plurality of bird feeders are provided together in a compact configuration for transport and / or storage. Optionally the plurality of bird feeders are substantially identical. Optionally the plurality of bird feeders comprises two bird feeders. Optionally the plurality of bird feeders are attached. Optionally the plurality of bird feeders are attached via their respective attachment means. Optionally the plurality of bird feeders are attached via a push-fit connection. Optionally, in the attached configuration, the openings or apertures of the bird feeders are proximal. Optionally the openings of the bird feeders are proximal and the recesses and projections of the respective attachment means are in push-fit connection. Optionally, in the attached configuration, the bird feeders together define a closed outer surface. Advantageously, the closed outer surface prevents exposure of the bird feed and protects the contents of the bird feeders. Optionally, in the attached configuration, the bird feeders together define a substantially spherical outer surface. According to another aspect of the invention there is provided a method of manufacturing a filled bird feeder, the method comprising manufacturing a bird feeder and at least partially filling the feed portion of the bird feeder with a feed mixture. Advantageously, the bird feeder can be manufactured e.g. as a single piece in a streamlined and efficient process. Optionally the method comprises injection moulding. Optionally the method comprises injection moulding the bird feeder. Optionally the method comprises placing the bird feeder on a surface. Optionally the method comprises placing the bird feeder on a flat surface. Optionally the method comprises placing the bird feeder on a flat surface such that the stabilising means contacts the flat surface. Optionally the method comprises placing the bird feeder on a flat surface such that the flat portion of the stabilising means contacts the flat surface. Optionally the method comprises preparing a feed mixture. Optionally the method comprises preparing a feed mixture in a hopper. Optionally the method further comprises filling the bird feeder. Optionally the method further comprises providing a feed mixture in the bird feeder. Optionally the method further comprises heating the feed mixture to a liquid or semiliquid state. Optionally the method further comprises heating the feed mixture to more than 35 degrees Celsius. Optionally the method further comprises heating the feed mixture to at least 37 degrees Celsius. Optionally the method further comprises inserting the feed mixture into the bird feeder. Optionally the method comprises at least partially filling the feed portion of the bird feeder with a self-levelling feed mixture. Optionally the inserting comprises dispensing or pouring. Optionally the method further comprises inserting the feed mixture into the feed portion. Optionally the method further comprises inserting the feed mixture into the bird feeder such that the feed mixture engages with the retaining means. Optionally the method further comprises inserting a fixed amount of the feed mixture into the bird feeder. Optionally the method further comprises inserting a 250 g of feed mixture into the bird feeder. Optionally the method further comprises inserting a predetermined volume of the feed mixture into the bird feeder. Optionally the method further comprises measuring the weight of the filled bird feeder. Advantageously, measurements of the weight of the bird feeder are used to ensure uniformity of the final product. Optionally the method further comprises cooling the feed mixture to a solid or semisolid state. Optionally the method further comprises cooling the feed mixture to less than 15 degrees Celsius. Optionally the method further comprises cooling the feed mixture to 8 degrees Celsius or about 8 degrees Celsius. Optionally the method further comprises attaching the bird feeder to one or more other bird feeders. Optionally the method further comprises attaching the bird feeder to another substantially identical bird feeder. Optionally the method further comprises attaching the bird feeder to another substantially identical bird feeder via their respective attachment means. Optionally the method further comprises attaching the bird feeder to another substantially identical bird feeder via a push-fit connection. Optionally the method further comprises attaching the bird feeder to another substantially identical bird feeder such that, in the attached configuration, the openings or apertures of the bird feeders are proximal. Optionally the method further comprises attaching the bird feeder to another substantially identical bird feeder such that, in the attached configuration, the bird feeders together define a closed outer surface. Optionally the method further comprises attaching the bird feeder to another substantially identical bird feeder such that, in the attached configuration, the bird feeders together define a spherical, substantially spherical, ovoidal or substantially ovoidal outer surface. Optionally the method further comprises packing the bird feeder. Advantageously, the uniformity of size allows the bird feeder to be more easily packed. Optionally the method comprises manufacturing, filling and / or packing a plurality of bird feeders. Optionally the method comprises manufacturing, filling and / or packing a plurality of identical bird feeders. According to another aspect of the invention there is provided a feed mixture for a bird feeder, the feed mixture comprising beef tallow, wheat flour, calcium carbonate and a mixture of seeds and / or dried bird food. Advantageously, the feed mixture is optimised for use in an automated, streamlined and efficient manufacturing process. According to another aspect of the invention there is provided a method of manufacturing a feed mixture for a bird feeder, the feed mixture comprising beef tallow, wheat flour, calcium carbonate and a mixture of seeds and / or dried bird food, the method comprising mixing the components of the feed mixture. Advantageously, the feed mixture is optimised for use in an automated, streamlined and efficient manufacturing process. Optionally the bird feeder comprises a feed mixture. Optionally the feed mixture is a high-energy feed mixture. Optionally the feed mixture is a suet mixture. Optionally the feed mixture is a high-energy suet mixture. Optionally the feed mixture is a high-energy suet mixture for wild birds. Optionally the feed mixture comprises a fat product. Optionally the fat product is beef tallow. Advantageously, beef tallow sets the hardest of available fats, so that the feed mixture will be effectively retained within the bird feeder. Optionally the feed mixture comprises at least 30% beef tallow. Optionally the feed mixture comprises no more than 40% beef tallow. Optionally the feed mixture comprises 30-40% beef tallow. Advantageously, 30-40% beef tallow ensures that the feed mixture can easily flow into and fill the bird feeder. Optionally the feed mixture comprises 34-36% beef tallow. Optionally the feed mixture comprises 35% beef tallow. Advantageously, this amount of beef tallow provides optimal viscosity of the feed mixture when it is in its liquid or semi-liquid state. Optionally the feed mixture is dosable. Advantageously, the feed mixture being dosable means that a plurality of bird feeders can easily be filled in an automated manufacturing process. Optionally the feed mixture is self-levelling. Advantageously, the feed mixture being self-levelling means that the top of the mixture does not need to be trimmed or levelled by hand. Optionally the feed mixture comprises a wheat product. Advantageously, the wheat product contributes to the optimal hardness of the feed mixture when it is in its solid or semi-solid state. Optionally the wheat product is flour. Optionally the wheat product is white pie flour or all-purpose flour. Advantageously, white pie flour or all-purpose flour does not alter the colour of the feed to a grey colour. Optionally the feed mixture comprises a colourant. Optionally the colourant is a dye, such as a food dye. Optionally the feed mixture comprises a filler material. Optionally the filler material is calcium carbonate. Advantageously, calcium carbonate provides nutritional benefit for birds, particularly for their beaks and bones and for egg development Optionally the feed mixture comprises calcium carbonate. Advantageously, calcium carbonate further helps to harden off the mixture when the mixture is in its solid or semi-solid state. Further advantageously, the calcium carbonate helps to increase the viscosity of the mixture when it is in its liquid or semi-liquid state. Optionally the feed mixture comprises particulate feed. Optionally the feed mixture comprises a plurality of particulate feeds. Optionally the particulate feed comprises seeds and / or nuts and / or dried bird food. Optionally the particulate feed comprises seeds. Optionally the seeds comprise sunflower seeds, black rapeseed, red millet, white millet and / or other small oil seeds. Optionally the particulate feed comprises nuts. Optionally the particulate feed comprises peanuts and / or other nuts. Optionally the particulate feed comprises dried bird food. Optionally the dried bird food comprises dried mealworm, dried insects and / or dried soldier fly larvae and / or other dried bird food. Drawings The invention will be more clearly understood by the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings, in which: Figure 1 is a rear perspective view of a bird feeder according to an aspect of the invention. Figure 2 is a cutaway perspective view of the bird feeder of figure 1. Figure 3 shows side, top, bottom and rear views of the bird feeder of figure 1. Figure 4 is a front view of the bird feeder of figure 1. Figure 5 is a detail view of the bird feeder of figure 1. Figure 6 is a side cross sectional view of the bird feeder of figure 1. Figure 7 is a detail cross sectional view of the bird feeder of figure 1. Figure 8A is a side view of a system of bird feeders according to an aspect of the invention. Figure 8B is a further side view of a system of bird feeders according to an aspect of the invention. Figure 9 shows a plurality of finishes for application to the surface of bird feeders according to an aspect of the invention. Figure 10 shows a method of producing a bird feed according to an aspect of the invention. Figure 11 is a front perspective view of a bird feeder according to an aspect of the invention. Figure 12 shows front, side and bottom views of the bird feeder of figure 11. Figure 13 is a front perspective view of a bird feeder according to an aspect of the invention. Figure 14 shows front, side and top views of the bird feeder of figure 13. Figure 15 is a front perspective view of a bird feeder according to an aspect of the invention. Figure 16 is a rear view of the bird feeder of figure 15. Figure 17 shows front, side and top views of the bird feeder of figure 15. Figure 18 shows front, side and top views of the bird feeder of figure 15. Figure 19 is a rear view of a bird feeder according to an aspect of the invention. Figure 20 shows top, side, front, side and bottom views of the bird feeder of figure 19. Figure 21 is a rear view of a bird feeder according to an aspect of the invention. Figure 22 shows top, side, front, side and bottom views of the bird feeder of figure 21. Detailed description Figure 1 shows a bird feeder 1 according to an aspect of the invention. The bird feeder 1 comprises a feed portion 2 configured to receive and retain a feed mixture for the feeding of wild birds. The bird feeder 1 also comprises an attachment arrangement 3 for attaching the bird feeder 1 to an external structure, such as a tree or a part thereof, or a branch, hook, nail or post. The bird feeder 1 is a unitary member. The bird feeder 1 being a unitary member removes the need to produce and combine multiple separate parts during manufacture of the bird feeder 1. In other words, the bird feeder 1 is able to perform the function of retaining bird feed for the feeding of wild birds while being formed of a single piece so that the manufacture of the bird feeder 1 is simplified. In preferable embodiments the bird feeder 1 is injection moulded and comprises injection moulding lines which are a hallmark of injection moulding processes. Other means for producing a unitary bird feeder are possible, for example 3D printing. The bird feeder 1 is a unitary member comprising a feed portion 2 and an attachment arrangement 3. The feed portion 2 is integrally formed with the attachment arrangement 3 such that the feed portion 2 and the attachment arrangement 3 are made from a single piece of one material and the feed portion 2 is attached to the attachment arrangement 3. The bird feeder 1 is biodegradable because the bird feeder 1 is made from and comprises a 100% biodegradable plant-based material. Use of a biodegradable material means that the bird feeder 1 is compostable. Therefore the bird feeder 1 can be disposed of in an environmentally-friendly way after use e.g. by composting or being disposed of with household food waste. The biodegradable material comprises a biodegradable polymer which can be injection moulded. The biodegradable material comprises up to 50% by weight of a biodegradable polymer, such as a natural biodegradable polymer made from sugar. Biodegradable polymers are polymers that break down after use via bacterial decomposition which produces natural by-products such as gases (CO2, N2), water, biomass, and inorganic salts. The biodegradable material also comprises plant waste, in particular at least 30% by weight of plant waste. In the most preferred embodiments, the plant waste comprises agricultural plant waste and / or cereal waste. The biodegradable material also comprises a filler or additive, in particular up to 25% by weight of filler or additive. The filler or additive can comprise natural starch and / or a calcium-based material such as calcium carbonate. The filler or additive provides additional strength to the material. Ideally the biodegradable material comprises food waste, in particular between 1% and 6% by weight of food waste. In preferred embodiments the biodegradable material comprises no more than 6% food waste by weight. The incorporation of food waste into the bird feeder 1 reduces the amount of biodegradable polymer required in the manufacture of the bird feeder 1, while using a small amount of finely-ground coffee grounds does not prevent the material from being injection moulded. In preferred embodiments the food waste is coffee grounds, which is added to the material and creates a brown colour. Brown is the most natural looking colour for the bird feeder and blends in to the surroundings in the garden environment thus reducing possible attraction of predators towards the bird feeder. In essence, use of coffee grounds gives the bird feeder a suitable natural-looking brown colour which will be seen by wild birds without attracting the attention of their predators, such as domestic cats. Table 1 shows example components of the biodegradable material used to manufacture the bird feeder 1: Component of biodegradable material Proportion Biodegradable polymer (e.g. a natural biodegradable polymer made from sugar) 45% by weight Plant waste (e.g. agricultural plant waste and / or cereal waste) 35% by weight Filler or additive (e.g. natural starch and / or a calcium-based material) 15 % by weight Food waste (e.g. coffee grounds) 5 % by weight Table 1: Example components of the biodegradable material As will be appreciated, the proportions of the above components can be adjusted for producing e.g. a harder or softer material, or a material of a different colour, as appropriate. For example, food waste such as coffee grounds may not be included, and the amount of plant waste and / or filler or additive may be increased accordingly. The bird feeder 1 comprises a feed portion 2 configured to receive a feed mixture, particularly a suet-cake feed mixture. In use (i.e. when the bird feeder 1 is being used to feed wild birds), a feed mixture is retained within the feed portion 2. In this configuration the bird feeder 1 is referred to as a ‘filled’ bird feeder i.e. the bird feeder 1 is filled with and / or retains at least some feed mixture. The feed portion 2 is made from a biodegradable material, in particular the biodegradable material described above. As shown in the views of figures 1-4, the feed portion 2 has an elliptical or substantially circular cross section and has a hemispherical or substantially hemispherical shape. Turning to the cross-sectional view of figure 2, the feed portion 2 defines a substantially hemispherical cavity 21. The feed portion 2 comprises a substantially hemispherical inner surface 22 and a substantially hemispherical outer surface 23. The inner surface 22 may be polished. The outer surface 23 may be provided with a pattern or texture thereon. As shown in figure 4, the feed portion 2 has a height H and a width W. In some embodiments the ratio between the height H and the width W of the feed portion 2 is near unity, e.g. 0.95:1. This makes the cross section of the feed portion elliptical in shape. As will be appreciated, other H:W ratios can be used, e.g. 1:1. The feed portion 2 comprises an aperture 24. The aperture 24 is ideally a curved, elliptical, generally circular or substantially circular opening. The aperture 24 is flat or substantially flat (i.e. defines a flat or substantially flat plane) and ideally comprises a curved, elliptical, generally circular or substantially circular peripheral portion 25. The aperture 24 is configured to allow the feed portion 2 to be filled with bird feed. Bird feed, such as a suitable feed mixture, is able to pass through the aperture 24 so that the feed portion 2 can be filled with bird feed via the aperture 24 and, in use, wild birds can access feed in the feed portion 2 via the aperture 24. Since the wall of the feed portion 2 has a fixed thickness, the ratio between the height and the width of the aperture 24 is the same as the ratio between the height H and the width W of the feed portion 2. As shown in e.g. figure 2, the feed portion 2 comprises a stabilising arrangement 25. The stabilising arrangement 25 allows the bird feeder 1 to rest on a surface in a stable manner, for example without rolling. The stabilising arrangement 25 allows the bird feeder 1 to remain at rest e.g. during filling of the bird feeder 1 with a feed mixture. The stabilising arrangement 25 comprises a flat portion 26. The opening or aperture 24 is opposite the flat portion 26. The opening or aperture 24 is on an opposite side of the feed portion 2 to the flat portion 26. The flat portion 26 is a flat surface or substantially flat surface. The flat portion 26 is a flat surface located on the outer surface 23 of the feed portion 2. The feed portion 2 is configured to retain a feed mixture, in use. In particular, the feed portion 2 comprises a retaining arrangement 27 to securely hold and retain a solid feed mixture within the feed portion 2 while the bird feeder is hanging from e.g. a tree or post. The retaining arrangement 27 ensures that feed mixture in the feed portion 2 does not move and / or fall out of the bird feeder 1 during use. This is especially useful e.g. during spells of hot weather where the suet-based feed mixture can soften and will be more susceptible to falling out of the feed portion The retaining arrangement 27 is located on the inner surface 22 of the feed portion 2. The retaining arrangement 27 comprises one or more protrusions 28 which extend away from an inner surface 22 of the feed portion 2 and towards the opening or aperture 24. In this example the retaining arrangement comprises five cylindrical or substantially cylindrical protrusions 28a-e (some of which are visible in e.g. figure 2) which extend from an inner surface of the feed portion 2. As shown in figure 2, the protrusions all extend the same distance, e.g. 10 mm, from the inner surface of the shell i.e. the protrusions 28a-e have the same length. In optional embodiments the retaining arrangement 27 additionally or alternatively comprises one or more fins, such as a plurality of fins extending from an inner surface of the feed portion 2. In further optional embodiments the retaining arrangement 27 comprises a high friction surface located on the inner surface 22 of the feed portion 2. In yet further optional embodiments the retaining arrangement 27 comprises a featured surface, such as a dimpled or patterned surface, located on the inner surface 22 of the feed portion 2. It will be appreciated that the purpose of the retaining arrangement 27 is to reduce and / or prevent movement of the solid feed mixture within the feed portion 2 and numerous combinations of the above-noted options are possible. Returning to figure 1, the bird feeder 1 comprises an attachment arrangement 3 for attaching the bird feeder 1 to one or more external structures such as a tree or a part thereof. For example the attachment arrangement 3 is configured to allow the bird feeder 1 to be securely fixed to a branch, hook, nail or post in a manner which allows birds to access the feed portion 2 and the feed mixture therein. In optional embodiments the external structure can be a loop, ring, string or rope to allow the bird feeder 1 to be hung or fastened to e.g. a branch, hook, nail or post. In further optional embodiments the external structure can be another bird feeder 1. The attachment arrangement 3 comprises a biodegradable material, such as the biodegradable material described above. The attachment arrangement 3 defines an aperture, hook or opening for receiving an external structure (such as a tree or a part thereof or a branch or post etc.) or a fixing arrangement (such as a loop, ring, string, hook, screw or nail etc.) to allow the bird feeder 1 to be attached to an external structure. As shown in figures 4 and 5, the attachment arrangement 3 is an elongate member 31 having opposing end portions 32a, 32b. The attachment arrangement 3 is connected to the feed portion 2 at each end portion 32a, 32b thereof. The attachment arrangement 3 is curved comprising a central curved portion 33. The attachment arrangement 3 is connected to the feed portion 2 at a peripheral edge of the feed portion 2. In particular, the attachment arrangement 3 is connected to the feed portion 2 at a peripheral edge of the opening or aperture 24 of the feed portion 2. An aperture 34 is defined by the feed portion 2 and the attachment arrangement 3. In particular, an aperture 34 is located between the outer peripheral edge of the opening or aperture 24 and an inner edge of the attachment arrangement 3. As shown in detail in figure 5, the attachment arrangement 3 of the bird feeder 1 comprises a recess 35 and a projection 36. The recess 35 and projection 36 are located on a single face 37 of the attachment arrangement 3. In particular, the recess 35 and projection 36 are located on a single front face 37 of the attachment arrangement 3. The recess 35 extends into the front face 37 of the attachment arrangement 3. The projection 36 extends out of or away from the front face 37 of the attachment arrangement 3. As shown in figures 6 and 7, in this example the projection 36 extends out of or away from the front face 37 of the attachment arrangement 3 by a distance which is less than the thickness of the attachment arrangement 3. In optional embodiments, the recess 35 may fully extend through the attachment arrangement 3. The attachment arrangement 3 comprises a flat front face 37 which is parallel or substantially parallel (and coincident) to the plane of the opening or aperture 24 of the feed portion 2 (see figure 6). The recess 35 has a complimentary shape to the projection 36. The recess 35 is shaped such that it would fit inside the projection 36, and does fit inside the projection of another similar bird feeder 1, in a push-fit or tight manner. In other words, the recess is shaped such that the configured to receive a projection of a further similar bird feeder 1 in a push-fit connection. Figures 8A and 8B show how the bird feeder 1 may be attached to a second, identical or complimentary bird feeder 1a. Figure 8A shows two identical bird feeders 1,1a just prior to their mutual attachment. In figure 8A the openings 24,24a of the respective bird feeders 1,1a are aligned and face each other as the bird feeders 1,1a move towards each other. Figure 8B shows the two bird feeders 1,1a after they have been attached via their respective attachment arrangements 3,3a. In particular, the projection of the first bird feeder 1 has been pushed into the recess of the second bird feeder 1a, and vice versa, forming two push-fit or friction connections which hold the bird feeders 1,1a together. In figure 8B the two bird feeders 1,1a are provided together in a compact configuration for transport and / or storage. In the attached configuration shown in figure 8B, the openings or apertures 24,24a of the bird feeders 1 are proximal. In the attached configuration, the bird feeders 1,1a together define a closed outer surface. The closed outer surface prevents exposure of any feed mixture within the bird feeders 1,1a (i.e. after they have been filled) and protects the contents of the bird feeders 1. In the attached configuration, the bird feeders 1 together define a substantially spherical or ovoidal outer surface. The attached configuration shown in figure 8B allows even numbers of bird feeders to be packed in a delivery or shipment container. For example, multiple pairs of attached bird feeders 1,1a can be held in a close-packed hexagonal configuration in a box or other storage arrangement. Returning to figure 1, the outer surface 23 of the bird feeder 1, or a part thereof, may be featured, textured or patterned. For example, the outer surface of the feed portion may comprise a featured surface, such as a dimpled or patterned surface. In figure 1 writing and / or symbols are formed on the outer surface 23. Optional patterns and textures for the outer surface 23 are shown in figure 9. If the outer surface 23 of the bird feeder is too smooth then wild birds would find it very difficult to cling and hold onto the bird feeder 1 and feed sufficiently. Providing a textured surface on the outer surface 23 of the bird feeder 1 creates a non-slip surface that wild birds can grab on to whilst feeding. Figure 10 is a schematic view of a method of manufacturing 100 according to an aspect of the invention. The result of the method 100 is a filled bird feeder i.e. a bird feeder 1 that has been filled (entirely or partially) with and / or retains at least some feed mixture. At step 102 the method 100 comprises manufacturing a bird feeder 1. In particular, the method 100 comprises manufacturing a unitary bird feeder 1 comprising a feed portion 2 configured to receive a feed mixture and an attachment arrangement 3 for attaching the bird feeder 1 to an external structure. Manufacturing the bird feeder 1 as a single unitary piece allows a more streamlined and efficient manufacturing process, without requiring the additional processing, machining and assembly steps typical of prior art bird feeders. Ideally the bird feeder 1 is manufactured from a biodegradable material, such as the biodegradable material described above, using injection moulding techniques. At step 104 the bird feeder 1 manufactured in step 102 is placed on a surface. In particular, the bird feeder 1 is placed on a flat or generally flat surface of a moving conveyor. When the bird feeder 1 is placed on the surface, the flat surface 26 of the stabilising arrangement 25 contacts the surface of the moving conveyor such that the bird feeder 1 is not liable to roll away during the filling process. At step 106 the method 100 comprises preparing a feed mixture. Step 106 can be carried out before, concurrently with or after steps 102 and / or 104. The feed mixture is prepared according to a preferred recipe, such as the following. A feed mixture according to an aspect of the invention comprises beef tallow, wheat flour, calcium carbonate and a mixture of seeds and / or dried bird food. The feed mixture is optimised for use in the present automated, streamlined and efficient manufacturing process. Table 2 is an example recipe for 250 g of bird feed, suitable for filling the feed portion 2 of the bird feeder 1 in a manufacturing process: Ingredient Amount Beef Tallow 90 g Wheat flour 60 g Calcium carbonate 50 g Kibbled wheat 20 g Mixed small seeds 30 g Table 2: An example feed mixture recipe for a single bird feeder, amounts corresponding to accuracy of one significant figure As will be appreciated, the quantities in the above recipe can be adjusted, and may be increased as appropriate for filling a plurality of bird feeders in an automated manufacturing process. The feed mixture is a high-energy suet mixture suitable for feeding wild birds. The feed mixture comprises a fat product, in this example beef tallow. Beef tallow sets the hardest of the commonly available fats, so that the feed mixture can be effectively retained within the bird feeder 1, in use. Optionally, the feed mixture comprises 30-40% beef tallow to ensure that the feed mixture has the correct consistency and can easily flow into and fill the bird feeder 1 during method 100. Ideally the feed mixture comprises 34-36% beef tallow, for example 35% beef tallow, which provides optimal viscosity of the feed mixture when it is in its liquid or semiliquid state. As is explained below, the feed mixture is dosable i.e. a plurality of bird feeders 1 can easily be filled in an automated manufacturing process. Furthermore, the feed mixture is self-levelling i.e. the top surface of the mixture settles flat after being dosed into a feed portion. This is beneficial because the mixture does not need to be trimmed or levelled by hand after being dispensed. The combination of a selflevelling mixture and the stabilising arrangement 25 means that no feed mixture will spill over and out of e.g. one side of the feed portion 2 during filling. The feed mixture comprises a wheat product which contributes to the optimal hardness of the feed mixture when it is in its solid or semi-solid state. In the present embodiment the wheat product is flour, in particular white pie flour or all-purpose flour. White pie flour or all-purpose flour does not cause the feed to take on a grey colour which is unattractive to birds. In an option the feed mixture can comprise a colourant such as a food dye which will change the colour of the feed mixture. The feed mixture comprises a filler material. In preferred embodiments the filler material is calcium carbonate which provides nutritional benefit for birds, particularly for their beaks and bones and for egg development. Calcium carbonate also helps to harden off the feed mixture when the mixture is in a solid or semi-solid state. Furthermore, calcium carbonate helps to increase the viscosity of the mixture when it is in a liquid or semi-liquid state. The feed mixture also comprises one or more particulate feeds which are nutritious for wild birds. In preferred embodiments the particulate feed comprises seeds and / or nuts and / or dried bird food. Seeds may be chosen from the group comprising sunflower seeds, black rapeseed, red millet, white millet and / or other small oil seeds. Nuts may be chosen from the group comprising peanuts and / or other nuts. Dried bird food can be chosen from the group comprising dried mealworm, dried insects and / or dried soldier fly larvae and / or other dried bird food. Returning to step 106 of the method 100 shown in figure 10, a feed mixture is prepared by mixing the component parts of the feed mixture together. Once mixed, the mixture is added to a hopper. As will be appreciated, some of the ingredients such as the fat product must be heated before mixing. Furthermore, the mixture must be kept at an elevated temperature, for example above 35 degrees, to allow it to be dispensed from the hopper and into the feed portion 2 of the bird feeder. At step 108 the bird feeder 1 is filled with the feed mixture prepared in step 106. The bird feeder 1 rests on the surface of a conveyor while a fixed amount of feed mixture in a liquid or semi-liquid state is dispensed or poured from the hopper into the feed portion 2. In a typical example process, 250 g of feed mixture is inserted into the feed portion 2 of the bird feeder 1. The process involves inserting a predetermined volume of feed mixture (i.e. a predetermined volume which corresponds to 250 g) into the feed portion 2 before measuring the weight of the filled bird feeder to confirm that the weight of the product is correct. This weighing process ensures the uniformity of the final product. Optionally the feed mixture moves under the force of gravity through the aperture 24 to fill or substantially fill the feed portion 2 of the bird feeder 1. The feed mixture settles in the feed portion 2 and engages with the retaining arrangement 27. In optimal embodiments the feed mixture is dispensed while the core temperature of the feed mixture is at least 37 degrees Celsius. At step 110 the bird feeder 1 with feed mixture therein is moved via the conveyor to a cooling station. At the cooling station the feed mixture is cooled to a solid or semisolid state. To ensure hardening, the feed mixture is cooled to less than 15 degrees Celsius, for example 8 degrees Celsius or about 8 degrees Celsius. Cooling takes approximately 30-40 minutes. At step 112 the method 100 comprises packing the bird feeder 1. For example the bird feeder 1 may be attached to a similar bird feeder 1a in the manner described above with respect to figures 8A and 8B and placed in a box or other shipment container. In optional embodiments the bird feeder may be placed within a box or other shipment container containing a suitable number of bird feeders, for example 1, 2, 4, 6, 8, 10 or 12 bird feeders. As will be appreciated, the uniformity of size allows the bird feeder 1 to be more easily packed with identical bird feeders than is the case for the prior art. Some or all of the steps of the method 100 may be repeated such that a plurality of identical bird feeders are manufactured, filled and / or packed, as required. Figures 11 and 12 show an alternative bird feeder 201 according to a further embodiment of the invention. The bird feeder 201 comprises a feed portion 202 configured to receive and retain a feed mixture for the feeding of wild birds. The bird feeder 201 also comprises an attachment arrangement 203 for attaching the bird feeder 201 to an external structure, such as a tree or a part thereof, or a branch, hook, nail or post. The bird feeder 201 is distinguished by the retaining arrangement 227 which includes a plurality of fins 227a and 227b. The fins 227a, 227b allow the feed mixture to be retained in the feed portion 202, in use. In particular, the fins 227a, 227b can securely hold and retain a solid feed mixture within the feed portion 202 while the bird feeder is hanging from e.g. a tree or post. The fins 227a, 227b are located on the inner surface 222 of the feed portion 202. The fins 227a, 227b extend away from an inner surface 222 of the feed portion 202 and towards the opening or aperture 224. Figures 13 and 14 show another alternative bird feeder 301 according to a further embodiment of the invention. The bird feeder 301 comprises a feed portion 302 configured to receive and retain a feed mixture for the feeding of wild birds. The bird feeder 301 also comprises an attachment arrangement 303 for attaching the bird feeder 301 to an external structure, such as a tree or a part thereof, or a branch, hook, nail or post. The bird feeder 301 is distinguished by the attachment arrangement 303 which is attached to the feed portion 302 at a single location and which comprises a single aperture 334. Furthermore, the feed portion 302 of the alternative bird feeder 301 is hemispherical and does not include a flat portion on which to rest. As will be appreciated, during manufacture the bird feeder 301 will need to be suitably retained during filling and cooling of the feed mixture. Figures 15 to 18 show an alternative bird feeder 401 according to a further embodiment of the invention. The bird feeder 401 comprises a feed portion 402 configured to receive and retain a feed mixture for the feeding of wild birds. The bird feeder 401 also comprises an attachment arrangement 403 for attaching the bird feeder 401 to an external structure, such as a tree or a part thereof, or a branch, hook, nail or post. The bird feeder 401 is distinguished by the retaining arrangement 427 which includes a plurality of fins 427a and 427b. The fins 427a, 427b allow the feed mixture to be retained in the feed portion 402, in use. In particular, the fins 427a, 427b can securely hold and retain a solid feed mixture within the feed portion 402 while the bird feeder is hanging from e.g. a tree or post. The fins 427a, 427b are located on the inner surface 422 of the feed portion 402. The fins 427a, 427b extend away from an inner surface 422 of the feed portion 402 and towards the opening or aperture 424. The bird feeder 401 of this embodiment is further distinguished by the attachment arrangement 403 which comprises a loop attached to the feed portion 402 at respective ends thereof. Furthermore, the feed portion 402 of the alternative bird feeder 401 is hemispherical and does not include a flat portion on which to rest. As will be appreciated, during manufacture the bird feeder 401 will need to be suitably retained during filling and cooling of the feed mixture. The outer surface of the feed portion 402 comprises one or more raised portions 455 to increase friction between neighbouring bird feeders or pairs of bird feeders while they are packaged, e.g. held in a close-packed hexagonal configuration in a box or other storage arrangement. Figures 19 and 20 show an alternative bird feeder 501 according to a further embodiment of the invention. The bird feeder 501 is similar to the bird feeder 1 previously described. The bird feeder 501 is distinguished by the writing on the back face of the feed portion. 5 Figures 21 and 22 show an alternative bird feeder 601 according to a further embodiment of the invention. The bird feeder 601 is similar to the bird feeder 1 previously described. The bird feeder 601 is distinguished by there being no writing on the back face of the feed portion. 10 The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail within the scope of the appended claims. For example, the bird feeder could be made from separate parts which are assembled and / or attached during manufacture. Other biodegradable or non-15 biodegradable materials may be used to form the bird feeder.

Claims

1. A bird feeder comprising a feed portion configured to receive a solid feed mixture, and an attachment means for attaching the bird feeder to an external structure, wherein the bird feeder is a unitary member formed from a biodegradable material, wherein the feed portion comprises retaining means for retaining the solid feed mixture in the feed portion , wherein the retaining means comprises one or more protrusions or fins extending away from an inner surface of the feed portion, wherein the feed portion is hemispherical or substantially hemispherical.

2. A bird feeder according to claim 1, wherein the biodegradable material comprises a biodegradable polymer.

3. A bird feeder according to claim 2, wherein the biodegradable material comprises food waste, such as coffee grounds.

4. A bird feeder according to any preceding claim, wherein the feed portion comprises an opening or aperture.

5. A bird feeder according to claim 4, wherein the feed portion comprises a stabilising means.

6. A bird feeder according to claim 5, wherein the stabilising means comprises a flat portion located on an outer surface of the feed portion, and wherein the stabilising means is located on an opposite side of the feed portion to the opening or aperture.

7. A bird feeder according to any preceding claim, wherein the attachment means is an elongate member having opposing end portions.

8. A bird feeder according to claim 7, wherein each end portion of the attachment means is connected to the feed portion.

9. A bird feeder according to any preceding claim, wherein the attachment means is connected to the feed portion at or near a peripheral edge of the opening.

10. A bird feeder according to any preceding claim, wherein the attachment means comprises a recess and a projection.

11. A bird feeder according to claim 11, wherein the recess is shaped such that the configured to receive a projection of a further similar bird feeder in a push-fit connection.

12. A bird feeder according to any preceding claim, wherein the inner surface of the feed portion comprises a dimpled or patterned surface.

13. A bird feeder according to any preceding claim, wherein the bird feeder is at least partially filled with a feed mixture.

14. A bird feeder according to claim 13, wherein the feed mixture comprises 30-40% beef tallow, for example 35% beef tallow.

15. A system comprising a plurality of bird feeders according to any preceding claim, wherein the plurality of bird feeders are attached to one another.

16. A system according to claim 15, wherein the openings of the bird feeders are proximal and the recesses and projections of the respective attachment means are in push-fit connection.

17. A method of manufacturing a filled bird feeder, the method comprising: manufacturing a bird feeder according to any one of claims 1 to 12; and at least partially filling the feed portion of the bird feeder with a feed mixture18. A method according to claim 17, wherein the step of manufacturing a bird feeder comprises injection moulding.

19. A method according to claim 17 or claim 18, wherein the method comprises at least partially filling the feed portion of the bird feeder with a self-levelling feed mixture.

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