Capture and Marking of Birds: Field Methods for European Starlings

Transcription

1 WLF 315 Wildlife Ecology I Lab Fall 2012 Capture and Marking of Birds: Field Methods for European Starlings Objectives: 1. Introduce field methods for capturing and marking birds. 2. Gain experience in trapping, handling and marking European starlings. 3. Mark starlings on campus for population estimation using mark-recapture analysis. A brief natural history of European starlings: European starlings (Sturnus vulgaris) are native to Eurasia, and were introduced to the United States in The initial release of birds in Central Park, New York City, was followed by rapid range expansion. Check your field guide for the current distribution of starlings in the U.S. Have starlings colonized all of the U.S. or only certain areas? What do starlings eat? How is their bill structure adapted to their feeding habits? Starlings are cavity nesters, but use a wide variety of nesting sights ranging from naturallyoccurring cavities in snags to suitable holes in man-made structures. Starlings exhibit a diverse array of behaviors. They usually breed monogamously, but have also been documented breeding cooperatively as well as promiscuously (Feare 1984). Additionally, some females parasitize the nests of conspecifics (others of the same species), placing their eggs into another female s nest. Starlings form large aggregations outside of the breeding season, and during winter, the birds are often observed feeding and roosting in very large flocks. Occasionally, starlings will form aggregations with other species such as grackles, robins, black birds, and cowbirds, which can number up to 10 million (Ehrlich et al. 1988). Because of their abundance and tendency to congregate, starlings are considered pests in many areas. One population estimate, made 15 years ago, put their numbers at around 200 million in the U.S. (Ehrlich et al. 1988). A more recent estimate is 140 million (Johnson and Glahn 1994). Although starlings feed on billions of insects annually, they also cause a significant amount of damage to livestock facilities and fruit orchards. Additionally, they compete with other cavity-nesting species such as woodpeckers, bluebirds, martins, and wood ducks. Starlings thrive in areas modified by humans, and reduction of human-starling conflicts will likely require a better understanding of the diverse ecological roles of the species (Johnson and Glahn 1994). For more information, read the essay by Ehrlich et al. (1988) posted on the class website or find it at (select Essays: Alphabetical Order and choose the link to European Starlings). There are a lot of other interesting essays from The Birder s Handbook also available at this web-site. References: Ehrlich, P. R., D. S. Dobkin, and D. Wheye The birder s handbook: a field guide to the natural history of North American birds. Simon and Schuster, Inc., New York, New York, USA. Feare, C The starling. Oxford University Press, New York, New York, USA. Johnson, R. J., and J. F. Glahn European starlings. Pages E109-E120 in S. E. Hyngstrom, R. M. Timm, and G. E. Larson, editors. Prevention and control of wildlife damage. University of Nebraska Press, Lincoln, USA.

2 Lab Exercise: Trapping and Banding European Starlings (Sturnus vulgaris) Reading Assignments (see class website for details): 1. European starling essay by Ehrlich et al. (1988). This essay is posted on the class website. 2. Portions of chapter 3 from the Techniques Manual. For this week s lab, you only need to read the portion of this chapter that pertains to birds pages Portions of chapter 9 (pages ) from the Techniques Manual. This chapter includes all animals, but pay particular attention to the sections about birds for this week s lab. Exercise Expectations: 1. Participate actively in the field exercise. 2. Read assigned material to learn capture and marking procedures for birds. 3. Complete data sheets for all birds that your group traps and marks. 4. Enter the data into an Excel file (template on website) and the file to the instructor (one file per group). Make sure that everyone in your group has participated and that their names are associated with the data. 5. Sign up for and attend at least 1 out-of-class banding session. You may sign up for as many as you like, but you must be available for at least 1 banding session outside of regular class times. Methods: 1. Form groups of +3 students. 2. Read this handout thoroughly and be sure you understand the methods before starting. Choose which student will accomplish each task. Rotate the duties with each capture. 3. Capture an individual bird by hand or using a fish net, and secure the bird from behind with a gentle grip (we ll go over the techniques for this during lab). 4. Identify the sex and age class of each bird, and record those data on the data sheet. 5. Work with your partners to complete and record the measurements for wing chord, culmen, and tarsus. Techniques for sexing, aging, and measuring are below. 6. Place the aluminum number band around the bird s right leg. Record the band number on the data sheet in the same row as other data. 7. Place the bird gently into the weighing tube and attach the tube to the Pesola scale. Record the weight. Grasp the bird and remove the tube completely before releasing the bird (make sure that people allow enough room for the bird to fly away). Weigh the empty tube and record the weight. Cautions: 1. Be calm, confident, and speak quietly when working with the animals. 2. Keep the bird under control until you are ready to release it. 3. When handling animals, do not touch your face (especially eyes and mouth) until after you have washed your hands with soap and water or a disinfectant. 4. Write legibly on the data sheets! If your handwriting is so poor that it is difficult to read, ask someone else to record data. Professionalism: When undertaking a study that involves capturing and marking wild animals, the reasons that necessitate handling the animals should be clearly defined, and potential negative effects of capture or marking should be considered. Any time an animal is handled, there is the risk of injury or death. Precautions should be taken to protect both the animals and people participating in the exercises. It is the responsibility of the wildlife professional to minimize the impact on animals and to ensure the safety of his or herself and others. Please be respectful of the birds, your classmates, and others during this lab exercise.

3 Data Recording: Record data for each trapping session on the data sheets in the appropriate columns. Record additional comments in the last column of the table. Such comments might include observations of anything that seems unusual about the animal, animal condition, interesting behaviors, comments about the data, or other problems. If you capture a bird that has already been banded (by us), record the band number, and then release the bird. Sexing and Aging Techniques: We are capturing starlings after the breeding season when they have completed the fall molt into their winter plumage. Starlings occasionally raise 2 or 3 clutches and we may see differences in the degree to which young of the year have attained winter plumage. The bottom line is that it can be difficult to assign some individuals to age classes, so make sure you check each bird out carefully. Use multiple characteristics and ask for help if you are unsure about aging a bird you have in hand. When in doubt, record age and/or sex as unknown. SEX Male: 1) Eye color is uniform dark brown. 2) Generally, fewer and smaller spots on breast. 3) Generally, more iridescence on head, nape, throat, breast, rump, and undertail coverts (both sexes have iridescence on the wings and back). Female: 1) Eye has a lighter ring around either the inner or outer the edge of the iris. 2) Generally, more and larger spots on breast. 3) Generally, less iridescence on head, nape, throat, breast, rump, and undertail coverts. AGE Adult (hatched in a previous year AHY): 1) Overall, more glossy and less spotted than juveniles. 2) No juvenal feathers behind the eye on the side of the head. 3) Pink legs. 4) Pointed tail feathers (retrices) with well-defined pale margins and usually a distinct black subterminal band on the retrices. 5) Pale feather tips on the belly and lower breast are divided by a pointed extension of the dark part along the rachis. Juvenile (hatched this year HY): 1) Generally, less glossy than adults and more spotted (immature females may be difficult to distinguish). 2) May have some juvenal plumage remaining, which is brown/gray with a lighter throat and streaking on the underparts. Presence of juvenal feathers behind the eye is definitive for juveniles. 3) May have brown or grayish legs (although often pink). 4) More rounded tips to retrices and less well-defined pale margins on the retrices. Retrices will have an indistinct dark subterminal band. 5) Pale feather tips on the belly and lower breast are not divided by a pointed extension of the dark part along the rachis. Length of iridescence on the throat feathers: Male: < 10 mm = immature Female: < 6 mm = immature mm = unknown 6-7 mm = unknown > 12 mm = adult >7 mm = adult

4 Measuring Techniques (see illustration): Collect the following measurements in millimeters using calipers. You may want to practice first with the calipers to be sure that you are reading the scale correctly. Be sure the calipers read 0 when fully closed. WING CHORD: The straight-line length of the wing in a closed position from the bend (bird's wrist) to the tip of the longest primary (flight) feather. The wing should NOT be flattened maintain the natural camber (curvature of the wing). CULMEN: The length from the tip of the bill in a straight line to the base of the feathers on the forehead. TARSUS: The distance from the joint between the tibia and metatarsus to the base of the middle toe.

5 Starling Banding Lab Exercise Lab Section: Monday or Tuesday Group Members: WLF Page of Date: REMEMBER: Band on Bird s Right Leg Band Number New Capture or Recapture (C or R) Sex (M or F) Age Class (J or A) Wing Chord Tarsus Culmen Weight w/ Tube (g) Empty Tube Weight (g) Comments