Town of Kiawah Island Winter Bird Banding Report

Transcription

1 Town of Kiawah Island Winter Bird Banding Report Prepared by: Aaron M. Given Assistant Wildlife Biologist Town of Kiawah Island

2 EXECUTIVE SUMMARY The Town of Kiawah Island completed its first winter season of bird banding in The banding station is located on Captain Sam s Spit on the west end of Kiawah Island. The winter banding season operated from 1 December to 15 March. A total of 388 birds of 11 species were banded. Yellowrumped Warblers were banded at an exceptionally high rate accounting for 96% of all birds banded. A couple of uncommon species for the Captain Sam s Banding Station were banded including a Field Sparrow and a Savannah Sparrow. Of all birds banded, 89% of them were second-year birds. Thirteen birds originally banded during the 2009 fall season were recaptured during the winter season. Among those recaptured were 4 species of migrants: House Wren (1), Swamp Sparrow (1), Hermit Thrush (1), and Yellow-rumped Warbler (4). The fact that these birds were recaptured in the winter after originally being banded in the fall is good evidence that there is some site fidelity for birds wintering at the Captain Sam s Banding Station. The extraordinarily high numbers of Yellow-rumped Warblers captured allows for a close examination of this species wintering at the CSBS. Many aspects of the Yellow-rumped Warbler population can and should be examined, such as their wintering ecology, over-winter survival, and site fidelity. ACKNOWLEDGEMENTS We would like to express gratitude to the Kiawah Conservancy for supporting our project by providing the funding to purchase mist nets, net poles, and other banding supplies and equipment. Additionally, we thank Kiawah Development Partners for allowing access to their property to band birds. We would like to thank Chris Snook, Will Oakley, Sarah Ernst, Tim Pifer, and Adam Nelson for volunteering their time to assist with our banding project. Without the help of these dedicated volunteers, this project would not have been possible. Front Photo: Yellow-rumped Warbler (After second-year, Male) Town of Kiawah Island Page 2

3 TABLE OF CONTENTS INTRODUCTION... 5 STUDY AREA... 5 METHODS... 6 RESULTS AND DISCUSSION... 6 Banding... 6 Recaptures... 8 Net Productivity... 9 Paid and Volunteer Hours CONCLUSION APPENDIX 1 - Summary of Species Captured at the Captain Sam s Banding Station APPENDIX 2 - Photographic Highlights Town of Kiawah Island Page 3

4 LIST OF FIGURES Figure 1. Location of the Captain Sam s Banding Station (CSBS)... 6 Figure 2. Net locations at the CSBS... 9 LIST OF TABLES Table 1. Top 5 species banded at Captain Sam s Banding Station (CSBS)... 7 Table 2. Age and sex of the top 3 species banded at CSBS... 8 Table 3. List of returns at CSBS... 9 Table 4. Net usage and capture rate at the CSBS Table 5. Paid and volunteers hours spent at CSBS Town of Kiawah Island Page 4

5 INTRODUCTION In 2008, Town of Kiawah Island wildlife staff designed the Kiawah Island Bird Monitoring Program. The program encompasses several projects which highlight Kiawah Island s birdlife. The projects include (1) summer point-counts of breeding songbirds, (2) call-playback surveys of breeding marsh birds, (3) nest monitoring of beach-nesting shorebirds, and (4) bird banding in the fall, winter, and spring. This report will only focus on the bird banding that occurred during the winter season. This was the first winter season of a long-term bird banding project on Kiawah Island. Bird banding on a large scale has never been performed on Kiawah Island before and it will provide valuable data on the species diversity and composition on Kiawah Island. Bird banding is also a significant tool used to assess the health and demographics of bird populations. Important information such as productivity, survivorship, and movements of many species can be attained through a banding program. All banding data collected is submitted to the Bird Banding Laboratory administered by the United States Geological Survey. The goals of winter bird banding project on Kiawah Island are to: Gather baseline information on resident and migratory birds using Kiawah Island. Collect data to enable long-term monitoring (i.e. population tends) of birds on Kiawah Island. Determine survival of songbirds, with a special focus on Yellow-rumped Warblers, wintering on Kiawah Island. Assess the effects of development on bird populations. Provide data to better manage habitat and guide future development plans. Contribute high quality data to the North American Bird Banding Program. STUDY AREA Captain Sam s Spit is a 45 acre strip of old vegetated dune ridges located at the west end of Kiawah Island ( N, W). It is bordered by the Atlantic Ocean to the south, the Kiawah River to the west and north, and the mainland of Kiawah Island to the east. Major habitat types include scrubshrub and high marsh. The overstory is made up of scattered slash (Pinus elliottii) and loblolly pine (Pinus taeda), eastern red cedar (Juniperus virginiana), and red bay (Persea borbonia). The dense midstory is dominated by wax myrtle (Myrica cerifera), sea ox-eye (Borrichia frutescens), marsh elder (Iva frutescens), and briars (Smilax spp.). The understory is dominated by marshhay cordgrass (Spartina patens), sweetgrass (Muhlenbergia filipes), sea lavender (Limonium carolinianum), and dune sandbur (Cenchrus tribuloides). The Captain Sam s Banding Station (CSBS) is centrally located and encompasses about 10 acres (Figure 1). Town of Kiawah Island Page 5

6 Figure 1. Map of Kiawah Island showing the location of the Captain Sam s Banding Station. METHODS Banding was scheduled once per month from 1 December through 15 March; however, no banding was conducted during December or March because of lack of personnel, scheduling conflicts, and weather. Mist nets (30 mm mesh) were used for all trapping. A standard mist net measures 12 meters long by 2.5 meters high and is made from black nylon material. Nets are stretched between two sections of ½ inch metal conduit and anchored to the ground by guy-lines attached to tent stakes. The conduit was painted brown to help conceal the poles. Nets were systematically placed in areas where significant bird activity was likely to occur. The standard setup for most of the season involved 8-10 nets. Some nets were not opened every session due to lack of personnel and/or excessive winds. Many of the same net locations from the 2009 fall season were used in the winter season. Nets were opened 30 minutes before sunrise and closed approximately 4-6 hours later. On a few occasions, all or some of the nets had to be shut down early because of rain, excessive wind, or an overabundance of birds. Nets were checked for birds about every 30 minutes. Captured birds were placed in cloth bags and transported back to the banding table. Birds were fitted with an aluminum leg band and their species, sex, and age were recorded. Morphological measurements including wing chord, fat score, and mass were also recorded. Pictures, if necessary, were taken and the birds were released. RESULTS AND DISCUSSION Banding Banding was conducted on two days during the winter season: 15 January and 19 February. Nets were open for a total of 12.5 hours resulting in 71.5 net-hours (a net-hour is a measure of effort and is equal to one standard mist net being operated for one hour). A total of 388 birds of 11 species were banded. Excluding recaptures, a capture rate of birds per 100 net-hours was achieved. Town of Kiawah Island Page 6

7 More than 100 birds were banded during each winter session. The first session on 15 January yielded 141 birds banded. Because an overwhelming number of birds were captured in a short period of time, the nets were closed down after 3.5 hours. In fact, one net had to be closed down right away because it had captured a large volume of birds (> 65 birds had to be released without being banded). The most successful day was on 19 February when 247 birds were banded. To mitigate for potentially capturing high numbers of birds simultaneously, 5 of the 10 nets were opened from 0630 to The remaining 5 nets were opened from 1100 to Species richness among banded birds was relatively low. The number of species banded for both sessions were 6 and 8, respectively. Yellow-rumped Warblers were by far the most numerous species accounting for 96% of the bandings for the entire winter season (Table 1). In January, incredible numbers of Yellow-rumped Warblers began arriving on Kiawah Island. Their numbers continued to build until early March and by mid-march the bulk of Yellow-rumped Warblers had left Kiawah Island. Table 1. Top 5 species banded at the Captain Sam s Banding Station during the winter season. Species Rank # Banded Yellow-rumped Warbler Gray Catbird 2 5 Ruby-crowned Kinglet 3 3 American Robin Species 5 1 Six species were banded only once: Hermit Thrush, Field Sparrow, Savannah Sparrow, Song Sparrow, White-throated Sparrow, and Common Grackle. For some of these species the fact that they were only banded once does not necessarily mean they are rare or uncommon. Hermit Thrush and Song Sparrow, most certainly, would have been captured more frequently with an increase in effort. Field Sparrows are fairly uncommon and a very good species to have captured in winter at CSBS. As expected, second-year individuals represented the majority, accounting for 89% of banded birds, while only 11% were after-second-year, and < 1% were of unknown age (Table 2). The skewed ratio of adult to young birds can be partially explained by the fact that during winter, there are more young individuals in the population as a result of the previous breeding season. A bird s first winter can be demanding and many of them do not survive. Additionally, short-distance migrants, such as the Yellowrumped Warbler, probably do not have as high of a mortality rate as long-distance migrants. The farther a bird migrates, the more dangers and uncertainty they will encounter. Nevertheless, these data may provide some insight into nesting success from one year to the next. Town of Kiawah Island Page 7

8 Table 2. Age and Sex of the top 3 species banded, and all species combined during the winter season at the Captain Sam s Banding Station. Species SY a ASY b Unknown Unknown Male Female Age Sex (% of total) (% of total) (% of total) (% of total) (% of total) (% of total) Yellow-rumped Warbler 334 (90) 37 (10) - 92 (25) 22 (6) 257 (69) Gray Catbird 5 (100) Ruby-crowned Kinglet 2 (67) 1 (33) - 3 (100) - - All Species 344 (89) 43 (11) 1 97 (25) 22 (6) 269 (69) a SY = Second Year (bird born the previous calendar year and generally before its first breeding season) b ASY = After Second Year (adult, bird born at least 2 calendar years before) For many species, sex cannot be reliable determined outside of the breeding season. This explains why 69% of banded birds could not be identified as either male or female. The plumage of the Yellowrumped Warbler is variable and complex, therefore all sexing criteria should match before a reliable determination is made. Because of this, a majority (69%) of Yellow-rumped Warlbers banded during the winter were of unknown sex. More study is needed in the sexing of Yellow-rumped Warblers in winter; consequently, this will be a major focus during next winter s banding season. Recaptures There were 21 recaptures of 7 species during the winter season. Recaptures are divided into local residents captured repeatedly, and migrant birds captured two or more times during the season. Migrant species made up 71% of all recaptures with Yellow-rumped Warblers being the most commonly recaptured species. Recaptures are divided into 4 categories: repeats, returns, foreign recaptures, and recoveries. Repeats are individuals that were recaptured during the same season they were banded. It also includes previously banded individuals captured repeatedly during the same season. Returns are individuals that were recaptured at least one season following banding. Foreign recaptures are individuals that are captured and released in a different location (10-minute block) than the location (10-minute block) in which they were banded. Recoveries are any encounter with a dead bird that is banded. There were 8 repeats of only 2 species during the winter season. All of the repeats were from migrant species that typically spend the winter on Kiawah Island. Yellow-rumped Warblers (7) made up the bulk of repeats, however three of these were recaptured on the same-day they were banded. There were 13 returns of 6 species during the winter season. All of the winter returns were from birds originally banded the previous fall indicating site fidelity occurs for some birds wintering at the CSBS. House Wren (1), Swamp Sparrow (1), Hermit Thrush (1), and Yellow-rumped Warbler (4) were the migrant species (Table 3) recaptured while Carolina Chickadees (4) and Northern Cardinals (2) were the two resident species recaptured. Town of Kiawah Island Page 8

9 Table 3. List of returns during the winter season. Entries are sorted by elapsed time. Resident birds were not included in this table. Band Original Banding Winter Species Number Date Recapture Date Time Elapsed Swamp Sparrow 11/05/09 02/19/10 3 months, 13 days Yellow-rumped Warbler 11/13/09 02/19/10 3 months, 5 days Yellow-rumped Warbler 11/13/09 02/19/10 3 months, 5 days Yellow-rumped Warbler 11/18/09 02/19/10 3 months, 0 days House Wren 10/29/09 01/15/10 2 months, 16 days Hermit Thrush 11/05/09 01/15/10 2 months, 9 days Yellow-rumped Warbler 11/24/09 01/15/10 1 month, 21 days Banded birds are infrequently encountered away from the location where they were banded. Any reports of foreign recaptures or recoveries are extremely significant. There were no foreign recaptures or recoveries during the winter season. Net Productivity Ten nets were placed in scrub/shrub habitat within old vegetated dunes and high marsh (Figure 2). Habitat diversity at the CSBS is fairly low, however the area is dominated by low growing shrubs and trees which makes it ideal for mist-netting birds. Figure 2. Location of mist-nets at the Captain Sam s Banding Station during the winter season. The overall capture rate for the winter season was new birds per 100 net-hours and an additional 29.3 birds per 100 net-hours were recaptures (Table 4). Nets # 4 and # 5 were the most productive with capture rates over 1000 birds per 100 net-hours. Both of these were placed in the Town of Kiawah Island Page 9

10 transition zone between dense wax myrtles and high marsh. They also had similar orientations with their placement starting perpendicular to dense shrubs and extending into high marsh. On 15 January, a large flock of Yellow-rumped Warblers (estimated at > 65 birds) were released unbanded from net # 9 because there were too many birds to safely handle at one time with the personnel available. Consequently, net #9 was closed for the rest of the day. Table 4. Net usage and capture rate during the 2009 fall season for the Captain Sam s Banding Station. Net # Net-Hours New Birds per 100 net-hours Recaptures Total Birds Captures New Total Total Paid and Volunteer Hours For a banding station to run efficiently, adequate personnel are required. A banding station needs properly trained people to remove birds from mist nets, correctly age and sex individuals, and safely apply the band to the bird s leg. Untrained personnel are also valuable as they can record data, take photos, organize banding supplies, and assist in setting up and taking down nets. A total of 82 hours were logged by two paid employees and five volunteers at the CSBS during the winter season (Table 5). Volunteers were those people that took part in the banding operation without being financially compensated. Paid hours were time spent by individuals being paid by the Town of Kiawah Island. Note that the values shown for hours only include those spent at the CSBS and do not include the extensive amount of time spent planning, entering and analyzing data, and writing reports. Town of Kiawah Island personnel duties and responsibilities: Aaron Given Master permit holder, supervisor of banding station, primary bird bander. Also responsible for data entry, data management, data analysis, and report writing. Jim Jordan Trained in bird extraction and banding birds, secondary bander. Also responsible for recording data in the field and updating the Town website with current banding totals. List of bird banding participants and hours contributed at the CSBS: Aaron Given (16), Jim Jordan (10), Chris Snook (16), Will Oakley (10), Sarah Ernst (10), Tim Pifer (10), Adam Nelson (10). Town of Kiawah Island Page 10

11 Table 5. Hours spent at the Captain Sam s Banding Station by paid employees and volunteers. PAID EMPLOYEES VOLUNTEERS # of Individuals Hours # of Individuals Hours CONCLUSION The data gathered from banding birds will add to the knowledge of numerous aspects of avian ecology on Kiawah Island including: species distribution, site fidelity, habitat quality, and population trends. Because this was the first winter banding season on Kiawah Island, there were many questions going into the season: (1) How many birds spend the winter on Kiawah Island? (2) What kind of species diversity will there be? (3) Is there strong site fidelity in winter? None of these questions will be answered in just one banding season, but the data collected does give some insight into them. Additionally, new questions are constantly being raised. The extraordinarily high numbers of Yellowrumped Warblers captured allows for a close examination of this species wintering at the CSBS. Many aspects of the Yellow-rumped Warbler population can and should be examined, such as their wintering ecology, over-winter survival, and site fidelity. Town of Kiawah Island Page 11

12 APPENDIX 1 Summary of Species Banded at the Captain Sam s Banding Station Town of Kiawah Island Page 12

13 BANDED BIRDS RECAPTURES SPECIES # of Capture Rate # of Capture Rate Individuals (# per 100 net-hours) Individuals (# per 100 net-hours) Carolina Chickadee House Wren Ruby-crowned Kinglet Hermit Thrush American Robin Gray Catbird Yellow-rumped Warbler Field Sparrow Savannah Sparrow Song Sparrow Swamp Sparrow White-throated Sparrow Northern Cardinal Common Grackle TOTAL Town of Kiawah Island Page 13

14 APPENDIX 2 Photographic Highlights from the 2009 Fall Season Town of Kiawah Island Page 14

15 White-throated Sparrow (Second-year, sex unknown). Captain Sam s Banding Station (02/19/10). Only 1 banded during the winter season. House Wren (Second-year, sex unknown). Cougar Island Banding Station (01/15/10). This was a recapture of a bird banded during the previous fall. Yellow-rumped Warbler (Second-year, male). Captain Sam s Banding Station (02/19/10). One of 371 banded during the winter season. Field Sparrow (After second-year, unknown sex). Captain Sam s Banding Station (02/19/10). Uncommon in winter on Kiawah Island, only 1 banded. Town of Kiawah Island Page 15