Method for determining black-mouth gull food source based on pill analysis

Abstract

The invention discloses a method for determining a black-mouth gull food source based on pill analysis, and belongs to the field of ecology. Determining a food pill collection area according to the black-mouth-gull-movement area, and collecting and storing a food pill sample; classifying and measuring food-borne animal residues in the food pill samples, and predicting category characteristics of food-borne animals in the food pill samples; food-borne animals in the nature are collected according to the black-mouth-gull-activity area, and category feature analysis is carried out; and evaluating the feeding preference of the black-mouth gull on the food-borne animals according to the variety characteristics of the food-borne animals in the food pill sample and the variety characteristics of the food-borne animals in nature. According to the method, the preference degree of the black-mouth gull on the main food source crabs is determined based on the black-mouth gull food pills, the preference characteristics of the black-mouth gull on the crabs can be effectively analyzed, and the method has important scientific significance on effective protection of wild animals, understanding of the functions of a coastal wetland ecosystem, evaluation of the quality of the coastal wetland ecosystem and subsequent protection of the black-mouth gull.

Description

Technical Field

[0001] The invention relates to the field of ecology, and in particular to a method for determining food sources of black-headed gulls based on food pellet analysis. Background Art

[0002] In the field of animal food source investigation, direct observation is usually used to observe animal feeding behavior. Observers observe animal feeding behavior in the wild and quickly and intuitively record the types and quantities of food. However, direct observation is easy for birds to detect and be disturbed. Secondly, it is difficult to fully grasp the types of food sources. Thirdly, it is usually only possible to qualitatively determine whether birds eat or not, but it is impossible to analyze the degree of preference of birds for specific crabs. Stable isotope analysis is a commonly used research method for food analysis. However, the bird sample collection process is relatively complicated, and it has a certain degree of impact on birds when taking samples such as blood, feathers and muscle tissue. In the calculation and analysis process, stable isotope analysis can only determine the main food composition and trophic level, but cannot analyze the degree of preference of birds for specific food sources. Pellets analysis is a method of analyzing the composition of bird food by analyzing the undigested food vomited by birds. This method can analyze the composition of bird food by analyzing the composition characteristics of undigested food in pellets without disturbing or harming birds, thereby determining the preference characteristics of black-headed gulls for food. This method can be used to analyze food pellets of shorebirds, red-crowned cranes and other birds, but there are no reports on its application in analyzing the food composition of black-headed gulls.

[0003] Liaohekou National Nature Reserve is located about 30km southwest of Panjin City, Liaoning Province. Its geographical coordinates are between 121°28′24.58″-121°58′27.49″ east longitude and 40°45′00″-41°05′54.13″ north latitude. It spans Panshan County and Dawa County. It is mainly composed of reed (Phragmites autralis) swamps, Suaeda salsa salt marshes, coastal mudflats, intertidal zones and shallow sea areas below 6m. The total area is 80,000 hectares, including 20,000 hectares of intertidal mudflats. It is a typical coastal wetland type reserve. Liaohekou Nature Reserve is located in the middle and north of the East Asian-Australasian (EAAF) migratory bird route. Its well-preserved estuarine wetland ecosystem provides rich resources for waterfowl and has become an important migratory stopover and breeding ground for a large number of waterfowl. The main protected objects of the reserve are rare and endangered water birds in the world, represented by the red-crowned crane (Grus japonensis) and the black-headed gull (Larus saundersi).

[0004] Black-headed gulls are a water bird of the Laridae family in the order Charadriiformes. Due to their small population, they are listed as vulnerable species by the World Conservation Union (IUCN), and the International Committee for the Protection of Birds (ICBP) has also listed them in the Red List of Endangered Birds. Black-headed gulls mainly inhabit coastal mudflats, swamps and estuaries, and have a clear preference for crustaceans, especially crabs. The breeding season is from May to June, and they often form small groups to nest centrally, usually in open coastal mudflats or intertidal highlands that are less affected by tides, where low salt-alkali plants such as Salicornia and Tamarix are distributed.

[0005] Food is the bond between animals and the environment. Therefore, studying the food preferences of black-headed gulls will help us further understand their foraging strategies and food selection mechanisms, thereby providing scientific and reasonable management measures for maintaining the development and protection of black-headed gull populations. Summary of the invention

[0006] The object of the present invention is to provide a method for determining the food source of black-headed gulls based on food pellet analysis, so as to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0008] A method for determining the food source of black-headed gulls based on food pellet analysis, comprising the following steps:

[0009] Determine the activity area of ​​black-headed gulls;

[0010] Determine the pellet collection area based on the black-headed gull's activity area, and collect and preserve pellet samples;

[0011] Classify and measure the remains of food source animals in food pellet samples, and predict the species characteristics of food source animals in food pellet samples;

[0012] Collect food source animals in nature according to the activity areas of black-headed gulls and analyze their species characteristics;

[0013] Based on the species characteristics of the prey animals in the food pellet samples and the species characteristics of the prey animals in nature, the feeding preference of black-headed gulls for prey animals was evaluated.

[0014] Preferably, the step of determining the activity area of ​​black-headed gulls specifically includes:

[0015] Track and determine the different activity areas of a group of black-headed gulls in a specific area, and divide the activity area types based on the results.

[0016] Preferably, the black-headed gull activity area at least includes the black-headed gull foraging area, the black-headed gull activity area and the black-headed gull nesting area; the food pellet collection area is determined according to the black-headed gull nesting area; and food source animals in nature are collected according to the black-headed gull foraging area.

[0017] Preferably, the food source animals include at least crabs.

[0018] Preferably, the step of classifying and determining the food source animal residues in the food pellet sample specifically comprises:

[0019] The crab chelicerae stumps in the food pellet samples were picked out, and the crab species were determined by the morphological differences of the digits and palmar segments of the chelicerae stumps. The number of digits and palmar segments of each type of crab in the food pellet samples was recorded, and the length of the palmar segment of the crab chelicerae and the width of the palm of the chelicerae were measured.

[0020] Preferably, the species characteristics of the food source animal at least include the species of the food source animal, the gender of the food source animal and the size of the food source animal.

[0021] Preferably, the feeding preference includes at least the black-headed gull's preference for the type, gender and size of the food source animals.

[0022] Preferably, the step of evaluating the black-headed gull's feeding preference for food source animals according to the species characteristics of the food source animals in the food pellet sample and the species characteristics of the food source animals in nature specifically includes:

[0023] To assess the preference of black-headed gulls for food animal species based on the proportion of different food animal species in food pellet samples and the proportion of different food animal species in nature.

[0024] To assess the preference of black-headed gulls for the sex of prey based on the proportion of prey of different sexes in the pellet samples and the proportion of prey of different sexes in nature.

[0025] Based on the size of the prey animal remains in the food pellet samples, the size of the prey animals in the food pellet samples was predicted, and based on the size of the prey animals in the food pellet samples, the preference of black-headed gulls for the size of prey animals was evaluated.

[0026] The embodiment of the present invention provides a method for determining the food source of black-headed gulls based on food pellet analysis, and determines the degree of preference of black-headed gulls for crabs, the main food source, based on the food pellets of the black-headed gulls. The preference characteristics of black-headed gulls for crabs can be effectively analyzed, which has important scientific significance for effectively protecting wild animals, understanding the functions of coastal wetland ecosystems, evaluating the quality of coastal wetland ecosystems, and for the subsequent protection of black-headed gulls. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a real picture of the Japanese big-eyed crab and its claw remains;

[0028] Figure 2 This is a real picture of Tianjin thick crab and its chelicerae remains;

[0029] Figure 3 This is the distribution diagram of the size of Tianjin thick crab in the food pellet samples;

[0030] Figure 4 This is the distribution diagram of the size of Japanese bigeye crabs in the food pellet samples. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] In one embodiment of the present invention, a method for determining the food source of black-headed gulls based on food pellet analysis is provided, which comprises the following steps:

[0033] S1. Determine the activity area of ​​black-headed gulls;

[0034] S2. Determine the pellet collection area according to the black-headed gull activity area, and collect and preserve pellet samples;

[0035] S3, classifying and measuring the remains of food source animals in the food pellet samples, and predicting the species characteristics of the food source animals in the food pellet samples;

[0036] S4. Collect food source animals in nature according to the activity areas of black-headed gulls and analyze their species characteristics;

[0037] S5. Evaluate the feeding preference of black-headed gulls for food animals based on the species characteristics of the food animals in the food pellet samples and the species characteristics of the food animals in nature.

[0038] It should be noted that pellet analysis refers to a method of analyzing the composition of bird food by analyzing the undigested food vomited by birds.

[0039] In a preferred embodiment of the present invention, the step of determining the activity area of ​​black-headed gulls, namely step S1, specifically comprises: tracking and determining different activity areas of a group of black-headed gulls in a specific area, and classifying the activity area types according to the results.

[0040] In a preferred embodiment of the present invention, the black-headed gull activity area at least includes the black-headed gull foraging area, the black-headed gull activity area and the black-headed gull nesting area; the food pellet collection area is determined according to the black-headed gull nesting area; and food source animals in nature are collected according to the black-headed gull foraging area.

[0041] Specifically, in step S1, the activity area of ​​the black-headed gull can be determined by direct observation. For example, the feeding behavior of the black-headed gull can be observed by using the naked eye, monocular, binoculars, cameras, video cameras and other equipment to determine the black-headed gull's foraging area, activity area, and nesting area; the food pellet collection area is determined according to the black-headed gull's activity area, and the food pellets are specifically selected to be collected in the nesting area;

[0042] In a preferred embodiment of the present invention, a GPS anklet (GPS-based smart positioning anklet) method can be used to track and determine the activity area of ​​a group of black-headed gulls.

[0043] In addition, in step S2, the collection of pellet samples is mainly concentrated in the nesting area of ​​black-headed gulls. In order to minimize the interference with bird activities, the pellet samples are collected when the black-headed gulls leave the nesting area, and relatively complete and fresh pellets are randomly selected for collection. The collected pellets are placed in a centrifuge tube, and the collection date and GPS location are recorded on the centrifuge tube for subsequent morphological measurements.

[0044] In a preferred embodiment of the present invention, the food source animals at least include crabs. It should be noted that in the following embodiments of the present invention, crabs are mainly used as examples for description, but are not limited thereto. The method provided by the present invention is also applicable to other food source animals.

[0045] In a preferred embodiment of the present invention, the steps of classifying and determining the food source animal residues in the food pellet sample specifically include:

[0046] The crab chelicerae stumps in the food pellet samples were picked out, and the crab species were determined by the morphological differences of the digits and palmar segments of the chelicerae stumps. The number of digits and palmar segments of each type of crab in the food pellet samples was recorded, and the length of the palmar segment of the crab chelicerae and the width of the palm of the chelicerae were measured.

[0047] Specifically, in step S3, the food source animal residue refers to the undigested food vomited by the black-headed gull. In practical applications, the crab chelae residues in the food pellet sample are picked out, and the number of crab knuckles and palmar segments is recorded. Image processing software such as ImageJ is used to measure the size of the crab residual limbs (the width of the palmar segment of the chelae and the length of the palmar segment). The measurement standards of the various parts of the crab residue are as follows: the palmar segment length of the chelae is measured from the outermost end of the immovable finger to the base of the palm, and the palmar segment width of the chelae is the widest distance of the palm. If the broken crab knuckles are encountered during the measurement process, the length of the crab chelae palmar segment is appropriately estimated to be extended according to the arc of the crab knuckles, and it is well marked. The embodiment of the present invention refers to the species characteristics of the food source animals in the food pellet sample with FS.

[0048] In a preferred embodiment of the present invention, the species characteristics of the food source animal at least include the species of the food source animal, the gender of the food source animal, and the size of the food source animal.

[0049] Specifically, in step S4, crabs and other food source animals in nature are collected using trap barrels in the foraging area of ​​black-headed gulls. In practical applications, crabs are captured in the habitat of Suaeda salsa and the intertidal zone of the tidal flats where black-headed gulls feed in large numbers; 20 trap barrels are arranged in the sampling area, and the interval between each trap barrel is not less than 20m; the crabs in the barrels are checked once a day, and the crabs are collected for 6 consecutive days. The captured crabs are placed in sealed bags and brought back to the laboratory for frozen storage. Assuming that the number of crab species is n, the total number of crab samples is not less than 30n, and the number of samples of each type of crab species is not less than 30. At the same time, the sample collection time and the trap barrel number are recorded; the collected crabs are rinsed with tap water; the crabs are placed in a culture dish, and the fresh weight and physical sign parameters are measured after natural air drying; the parameters of physical sign measurement include: carapace width, carapace length, and the length and width of the chelicerae. In the embodiment of the present invention, NS refers to the species characteristics of food source animals in nature; wherein, the measurement method of each parameter is as follows:

[0050] Carapace width measurement: Place the crab horizontally with its back facing upwards, and place a vernier caliper perpendicular to the crab's back in the middle of the crab's width axis for measurement. During the measurement process, the maximum width is taken as the crab's carapace width.

[0051] Carapace length measurement: Place the crab horizontally with its back facing upwards, and place a vernier caliper between the central notch of the crab's long-axis frontal teeth and the middle of the rear edge of the cephalothorax to measure. The measured value is the crab's carapace length.

[0052] Measurement of the cheliceral joints: including length and width. The length is measured using a vernier caliper (0.1 mm), with one end aligned with the movable part of the wrist and palm of the chelicer, and the other end aligned with the fingertip. The vernier caliper is measured perpendicular to the outer edge of the finger joints, and the widest part of the chelicer is taken as the width of the cheliceral joints.

[0053] In addition, the method for identifying crab species is as follows: Use visual inspection to identify crab species. For example, the main crab species near the Liaohe River Estuary Wetland are Japanese big-eyed crabs and Tianjin thick crabs. Japanese big-eyed crabs and their chelicerae are as follows: Figure 1 As shown in the figure, the Tianjin thick crab and its chelicerae remains are as follows Figure 2 As shown. The characteristics of the chelipeds of different species of crabs vary greatly: among them, the chelipeds of the Japanese big-eyed crab are large, the dorsal and ventral margins of the long segment are granular and short hairy, the back of the wrist segment has 1-2 granular ridges, the front and rear margins of the long segment are granular, the knuckles are flat, and the front and rear margins have short hairs. The length of the palm is about 2.1 times the height, and the surface is relatively smooth. Both fingers are bent downward, and there is no gap between the fingers. There is a large transverse tooth at the base of the inner edge of the movable finger, and the inner edge of the immovable finger has protruding teeth of varying sizes near the middle and middle parts; the inner end of the ventral margin of the long segment of the chelipeds of Tianjin thick crab has a longitudinal pronunciation ridge. The palm segment is high and smooth, and the dorsal margin is sharply raised. The pronunciation ridge on the inner side of the long segment is shorter and thicker than the latter two types, the palm segment is high and smooth, and the dorsal margin of the movable finger is generally straight.

[0054] According to the number of crab species collected as food sources, the proportion of each type of crab in the food source was calculated using formula (1).

[0055]

[0056] Where: NSspecies i represents the proportion of the i-th type of crab in the food source, N Ni Represents the number of samples of the i-th type of crab in natural food sources.

[0057] The method for determining the sex of crabs under the same species is as follows: Let the length of the chelicerae of the jth sex of the i-th species be AZc ij AZk is the width of the chelipeds. ij , using the length of the crab chelicerae segment AZc of the food source sample ij , Chelipeds palm width AZk ij The data were used as the parent sequence, and the FISHE discriminant method was used to establish the sex discriminant equations of different types of crabs. The difference between the female and male discriminant equations was calculated, with positive values ​​representing females and negative values ​​representing males.

[0058] According to the number of crabs of each sex collected from the natural food source, the proportion of female and male crabs in the natural food source is calculated, as shown in formula (2):

[0059]

[0060] Where: NSsex ij represents the proportion of crabs of the i-th species and the j-th sex in the natural food source; i=1 is Tianjin thick crab, i=2 is Japanese big-eyed crab; j=1 is female crab, j=2 is male crab; N Nij Represents the number of samples of crabs of the i-th species and the j-th sex in natural food sources.

[0061] The correlation between the morphological indicators of male and female crabs under the species is as follows: the carapace width and carapace length represent the crab size. Based on the classification of crab species and sex, the correlation between the length and width of the chelicerae palm section of crabs and their carapace length and width is established. The linear regression analysis method is used to determine the functional relationship between the chelicerae characteristic parameters of male and female crabs and the crab size parameters, and the linear regression equations shown in formulas (3) and (4) are obtained:

[0062] JK ij =a ij1 *AZc ij +b ij1 *AZ ij +C ij1 (3)

[0063] JC ij =a ij2 *Acij +b ij 2*AZk ij +c ij2 (4)

[0064] Where: JK represents the width of the crab carapace in the food source, JC represents the length of the crab carapace in the food source; i represents the species; when i=1, it represents Tianjin thick crab; when i=2, it represents Japanese big-eyed crab; j represents sex; when j=1, it represents female crab; when j=2, it represents male crab; a ij1 、b ij1 、c ij1 is the linear regression equation coefficient of the carapace width, chelicerae palm length, and chelicerae palm width of the i-th species of crab j-th sex; a ij2 、b ij2 、c ij2 is the coefficient of the linear regression equation of the carapace length, chelicerae palm length and chelicerae palm width of the jth sex of the i-th species of crab.

[0065] After distinguishing the sex of the crabs eaten by the black-headed gulls by the FISHE discrimination method, the claw characteristic parameters of female and male crabs are substituted into the corresponding linear regression equation to calculate the size of the crabs eaten by the black-headed gulls.

[0066] Furthermore, if there is multicollinearity between parameter variables, ridge regression is used to enhance the model's anti-interference ability and increase model stability. If the parameter regression coefficient is not significant, the regression coefficient is recorded as 0.

[0067] In a preferred embodiment of the present invention, the feeding preference at least includes the black-headed gull's preference for the type, gender and size of the food source animal.

[0068] In a preferred embodiment of the present invention, the step of evaluating the feeding preference of black-headed gulls for food source animals according to the species characteristics of the food source animals in the food pellet sample and the species characteristics of the food source animals in nature, i.e., step S5, specifically comprises:

[0069] S51. Evaluate the preference of black-headed gulls for the types of food animals based on the proportion of different types of food animals in food pellet samples and the proportion of different types of food animals in nature.

[0070] S52. Evaluate the preference of black-headed gulls for the sex of food animals based on the proportion of food animals of different sexes in food pellet samples and the proportion of food animals of different sexes in nature.

[0071] S53. Predict the size of the food animals in the food pellet samples based on the size of the food animal remains in the food pellet samples, and evaluate the preference of black-headed gulls for the size of food animals based on the size of the food animals in the food pellet samples.

[0072] In practical applications, the frequency of occurrence of crab species and sex in all samples was counted in nature and in pellet samples, and the feeding characteristics of black-headed gulls on crab species and sex were calculated using formulas (6) and (7). The calculation formula is:

[0073]

[0074] Where: FSspecies i N represents the proportion of the i-th type of crab in the pellet sample, Fi Indicates the number of samples of the i-th type of crab in the pellet sample. ij N represents the proportion of crabs of the i-th species and j-th sex in the pellet sample, Fij Represents the number of crab samples of the i-th species and the j-th sex in the food pellet sample.

[0075] In step S5, the higher the preference, the higher the preference of the black-headed gull for the food source crab. Among them, FS and NS respectively reflect the types of food when the black-headed gull is feeding and the types and proportions of food in nature. The embodiment of the present invention establishes multiple new indicators such as crab type and gender feeding preference and feeding probability to evaluate the black-headed gull's feeding preference.

[0076] Specifically, in step S51, the evaluation formula of the black-headed gull's preference for crab species is as follows:

[0077]

[0078] Where, TGIspecies i represents the preference of black-headed gulls for the i-th species of crab; when TGIspecies i >1, indicating a strong preference for this type of crab; when TGIspecies i =1, indicating no preference for this type of crab; when TGIspecies i When <1, it indicates a weak preference for this type of crab.

[0079] The formula for calculating the probability of black-headed gulls feeding on the i-th type of crab is as follows:

[0080]

[0081] Where Pspecies i It represents the probability of black-headed gulls eating the i-th species of crab when faced with multiple crab species.

[0082] In step S52, the evaluation formula of the black-headed gull's preference for the gender of the crab is as follows:

[0083]

[0084] Where, TGIsex ij represents the preference of black-headed gulls for crabs of the i-th species and the j-th sex; when TGIsex ij >1, indicating a strong preference for crabs of that sex; when TGIsex ij =1, indicating no preference for crabs of that sex; when TGIsex ij When <1, it indicates a weak preference for crabs of that gender.

[0085] The formula for calculating the probability of black-headed gulls feeding on crabs of the i-th species and the j-th sex is as follows:

[0086]

[0087] Where Psex ij It represents the probability of eating the jth sex crab when facing the i-th type crab.

[0088] In step S53, the method for evaluating the preference of black-headed gulls for the size of crabs is as follows: based on the characteristic parameters of the chelicerae in the pellet samples, the above linear regression equations (3) and (4) are used to calculate the length and width of the crab carapace to determine the size preference characteristics of the crabs.

[0089] The above method was applied to evaluate the preference of black-headed gulls for crabs and other food animals in Liaohe Estuary Wetland, as follows:

[0090] 1. Use the FISHE discrimination method to establish the sex discrimination equation of Tianjin thick crab and Japanese big-eyed crab (as shown in Table 1).

[0091] Table 1 Sex discrimination analysis of Tianjin thick crab and Japanese big-eyed crab

[0092]

[0093] 2. Establish the correlation between the claw parameters of food crabs and their carapace length and width (as shown in Table 2).

[0094] Table 2 Relationship between size and chelicerae of crabs of different species and sexes

[0095]

[0096] 3. Prediction of crab species, sex and size in food pellet samples (results are shown in Table 3).

[0097] Table 3 Prediction of crab characteristics in food pellets

[0098]

[0099]

[0100] 4. Calculate the crab species preference of black-headed gulls in the Liaohe Estuary Wetland (the results are shown in Table 4).

[0101] Table 4 Crab species preference of black-headed gulls in Liaohe Estuary Wetland

[0102]

[0103] 5. Calculate the preference of black-headed gulls for the gender of crabs in the Liaohe Estuary Wetland (the results are shown in Table 5).

[0104] Table 5 Sex preference of black-headed gulls for crabs in Liaohe Estuary Wetland

[0105]

[0106] 6. Calculate the crab size preference of black-headed gulls in Liaohe Estuary Wetland (results are as follows Figure 3 and Figure 4 shown).

[0107] from Figure 3 and Figure 4 It can be seen that the carapace width of Tianjin thick crab eaten by the black-headed gulls in the Liaohe Estuary Wetland ranges from 13.3-28.6mm, and the carapace length ranges from 11.3-22.1mm; the carapace width of Japanese big-eye crab eaten by the black-headed gulls in the Liaohe Estuary Wetland ranges from 7.1-47.3mm, and the carapace length ranges from 8.5-32.3mm.

[0108] In summary, the embodiment of the present invention proposes for the first time to calculate the preference of black-headed gulls for crab species, crab gender, and crab size based on the properties of food source fragments in food pellets, using the food source preference calculation formula established for the first time, which is of great significance to practical scientific research. Specifically, the embodiment of the present invention extracts the biological numerical attributes of food source crabs, uses the morphological characteristics of crab fragments in food pellets, and creates a preference formula for black-headed gulls for crab species, gender, and size, which can effectively analyze the black-headed gulls' preference characteristics for crabs.

[0109] Based on the above-mentioned ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above-mentioned description. The technical scope of the present invention is not limited to the contents of the specification.

Claims

1. A method for determining the food source of black-headed gulls based on food pellet analysis, characterized in that: The following steps are involved: Determine the activity area of ​​black-headed gulls; Determine the pellet collection area based on the black-headed gull's activity area, and collect and preserve pellet samples; Classify and measure the remains of food source animals in food pellet samples, and predict the species characteristics of food source animals in food pellet samples; Collect food source animals in nature according to the activity areas of black-headed gulls and analyze their species characteristics; Based on the species characteristics of the prey animals in the food pellet samples and the species characteristics of the prey animals in nature, the feeding preference of black-headed gulls for prey animals was evaluated.

2. The method for determining the food source of black-headed gulls based on food pellet analysis according to claim 1, characterized in that: The steps to determine the activity area of ​​black-headed gulls include: Track and determine the different activity areas of a group of black-headed gulls in a specific area, and divide the activity area types based on the results.

3. The method for determining the food source of black-headed gulls based on food pellet analysis according to claim 1, characterized in that: The black-headed gull activity area at least includes the black-headed gull foraging area, the black-headed gull activity area and the black-headed gull nesting area; the food pellet collection area is determined according to the black-headed gull nesting area; Collect food animals in nature according to the foraging areas of black-headed gulls.

4. The method for determining the food source of black-headed gulls based on food pellet analysis according to claim 1 or 3, characterized in that: The food source animals include at least crabs.

5. The method for determining the food source of black-headed gulls based on food pellet analysis according to claim 4, characterized in that: The steps for classifying and determining the food animal remains in the pellet samples specifically include: The crab chelicerae stumps in the food pellet samples were picked out, and the crab species were determined by the morphological differences of the digits and palmar segments of the chelicerae stumps. The number of digits and palmar segments of each type of crab in the food pellet samples was recorded, and the length of the palmar segment of the crab chelicerae and the width of the palm of the chelicerae were measured.

6. The method for determining the food source of black-headed gulls based on food pellet analysis according to claim 4, characterized in that: The species characteristics of the food source animal at least include the species of the food source animal, the gender of the food source animal, and the size of the food source animal.

7. The method for determining the food source of black-headed gulls based on food pellet analysis according to claim 6, characterized in that: The feeding preference at least includes the black-headed gull's preference for the type, gender and size of the food source animals.

8. The method for determining the food source of black-headed gulls based on food pellet analysis according to claim 7, characterized in that: According to the species characteristics of the food source animals in the food pellet samples and the species characteristics of the food source animals in nature, the steps for evaluating the feeding preference of black-headed gulls for food source animals specifically include: To assess the preference of black-headed gulls for food animal species based on the proportion of different food animal species in food pellet samples and the proportion of different food animal species in nature. To assess the preference of black-headed gulls for the sex of prey based on the proportion of prey of different sexes in the pellet samples and the proportion of prey of different sexes in nature. Based on the size of the prey animal remains in the food pellet samples, the size of the prey animals in the food pellet samples was predicted, and based on the size of the prey animals in the food pellet samples, the preference of black-headed gulls for the size of prey animals was evaluated.

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