City of Richmond TREE SWALLOW NEST BO X PROJECT 2021 Summary Report In 2021, the City of Richmond and Melissa Hafting initiated a Tree Swallow Nest Box Project at three parks: Garden City Lands, Garden City Park , and Terra Nova Natural Area The objective of the project was to provide additional nest sites for Tree Swallows because they are declining and there is a lack of natural nesting cavities. Melissa Hafting came up with this idea in 2020 during the Cov id - 19 pandemic. Nest box installation followed best practices to Background Ilya Povalyaev , BSc, RPBio & Melissa Hafting , BSc help protect nesting swallows from terrestrial predators such as rats and racoons and from aggressive bird species such as House Sparrows. Nest boxes were checked on May 15 - 16, June 5, and July 17 - 18 and cleaned at the end of the nesting season . Data was entered into Project N estwatch for Birds Canada and the results are summarized in this report . This is the first year of the Tree Swallow nes t box program for the City of Richmond. Photo: Melissa Hafting 2 Each spring, Tree Swallows arrive in Greater Vancouver in late February or March. 1 Male tree swallows usually arrive and defend a nest cavity up to several days prior to female arrival. 2 Pairing begins as soon as females arrive on the breeding grounds. Pairs deposit a few pieces of nesting material in the nes t cavity shortly after pair formation, but actual nest construction begins several weeks later and is completed almost entirely by females. 2 Nests are constructed from grasses and extensively lined with feathers of other species. 2 Egg laying typically o ccurs throughout May and June, but can begin as early as mid April. 1 Clutch size is usually 4 to 6 eggs, with one egg laid per day. 1,2 Typically only females incubate the eggs, starting on the day the penultimate egg is laid and lasting for 14 to 16 days. 1 ,2 The male does not feed the incubating female. The female incubates in bouts of 11 to 15 minutes, followed by 7 to 9 minutes off the nest. 2 Second broods have been assumed to be very rare in northern portions of range and is usually associated with repla cement clutches after the failure of the first clutch. 2 Following hatching, nestlings have poor thermoregulation during their first 7 to 8 days of life and require frequent brooding by the female to maintain body temperature. 2 Parents begin feeding nestli ngs as soon as they hatch and continue until nest departure. Parents carry food in their bill and place it directly into the open mouth of a begging nestling. During periods of peak nestling demand, parents may feed as many as 6,000 to 7,000 insects in a s ingle day. 2 Nestlings usually depart from the nest 15 to 25 days after hatching. 1 Young can fly when they leave the nest for the first time and generally do not return to the nest once they have flown. Tree Swallow Nesting Ecology GLOSSARY Clutch The number of eggs laid by one bird during one nesting season. Fledge To leave the nest once flight capable. Occupancy Rate The proportion of nest boxes that were used for nesting. Nesting Success Rate The proportion of eggs that hatched and ultimately fledged. Photo: Ilya Povalyaev 3 Three nest boxes were installed at Garden City Park and one of which (box #3) was occupied by Tree Swallows. Four eggs were present in box #3 on 5 June 2021. On 17 July 2021, two dead nestlings were found in the box, but the two others are assumed to have fledged. Tree Swallow occupancy rate at Garden City Park was 33% and nesting success was 50%. Garden City Park Garden City Park Twenty nest boxes were installed at Garden City Lands, five of which were occupied by Tree Swallows. Adult tree swallows were observed entering box #16 on 5 June 2021, however its contents could not be checked d uring the nesting season because it was installed in the middle of the pond and was not accessible. By late summer, the pond had dried up and the box was checked on 18 July 2021 at which time a fully constructed but empty nest was observed, indicating that all nestlings had successfully fledged. Although clutch size at box #16 was unknown, it is assumed to have been 5 based on the observed clutch size of other nests in the program. On 5 June 2021 box #8 had 4 eggs, box #18 had 5 eggs and box #12 had 5 nes tlings. On 18 July 2021, two dead nestlings were found in box #18 while all others had fledged. Additionally, a new clutch was initiated in box #3 since the previous check and 4 nestlings were present. All four nestlings fledged from box #3 by August 8. I n total, 21 young fledged from nest boxes at Garden City Lands. Tree Swallow occupancy rate at Garden City Lands was 25% and nesting success was 91.3%. Figure 1 : Nes t box locations at Garden City Park (top) and Garden City Lands (bottom). Yellow placemarks indicate locations of occupied nest boxes and white placemarks indicate locations of unoccupied nest boxes. Letters n ext to the placemarks correspond to the nest box number. Garden City Lands 4 Terra Nova Natural Area E ighteen nes t boxes were installed at Terra Nova Natural Ar ea, eight of which were occupied by Tree Swallows. Tree Swallow eggs were present in five boxes at Terra Nova on May 15. On June 5, five boxes contained 5 nestlings and one box contained 5 eggs. Additionally, box #3 was also occupied but clutch size could not be determined because the female was sitting on the nest at the time of the check. Nesting was initiated later at box #10; no eggs were present on June 5, but two nestlings were observed on July 17. It is assumed that the clutch size at boxes #3 and # 10 was 5. On July 17, there were four dead nestlings at box #8 and 2 dead nestlings at box #18. Nestlings had fledged from the other boxes. In total, 31 young fledged from nest boxes at Terra Nova. Tree swallow occupancy rate was 44.4% and nesting success was 77.5%. Additionally, four nest boxes at Terra Nova were occupied by Black - capped Chickadees. Although they are not the focal species of the nest box program, chickadees are native cavity nesters and their utilization of nest boxes is considered benef icial. With an average clutch size of six, chickadees are assumed to have fledged 22 young from four boxes (one dead nestling and one non - viable egg were observed in box #6). Chickadees are not believed to have excluded Tree Swallows from nest boxes at Ter ra Nova because there were multiple unoccupied nest boxes remaining. Figure 2 : Nes t box locations at Terra Nova Natural Area Yellow placemarks indicate locations of nest boxes occupied by Tree Swallows, green placemarks indicate locations of nest boxes occupied by Black - capped Chickadees, and white placemarks indicate locations of unoccupied nest boxes. Letters next to the placemarks correspond to the nest box number. Left: Black - capped Chickadee nestlings at Terra No va box #5. 5 Tree Swallow nesting was observed in all three parks where nest boxes were installed by the City of Richmond: Garden City Park, Garden City Lands, and Terra Nova Natural Area. Fourteen of 41 (34.1%) boxes were used by Tree Swallows and an estimated 54 young fledged. Nesting success rate, measured as the proportion of eggs that resulted in fledged young, was 80.6%. Metrics for each park are presented in Table 1. Occupancy rate was highest at T erra Nova, where Tree Swallows were traditionally most common prior to the nest box program. Success rate was highest at Garden City Lands, possibly because many of the nests were initiated later in the summer compared to Terra Nova and may have been less impacted by the heat wave. Successful nesting by Tree Swallows at Garden City Park and Garden City Lands is particularly notable because Tree Swallows were not previously known to nest at either location due to limited suitable natural nest sites. Table 1 : Summary of Tree Swallow Nesting Success in 2021. Location Number of Nest Boxes Number of Nest Boxes Used Occupancy Rate (%) Number of Eggs Number of Young Fledged Success Rate (%) GCP 3 1 33.3 4 2 50.0 GCL 20 5 25.0 23 21 91.3 TN 18 8 44.4 40 31 77.5 Total 41 14 34.1 6 7 5 4 80 .6 GCP = Garden City Park; GCL = Garden City Lands; TN = Terra Nova Natural Area. It is believed that most of the observed Tree Swallow nestling mortalities were attributed to the intense and sustained heat wave that occurred throughout British Columbia from late June through mid - July of 2021. During this period, daily temperatures highs in Vancouver frequently exceeded 30 ° C. 3 The heat wave was a 1 in 1,000 year event, made 150 times more likely by clima te change. 4 This highlights the vulnerability of nesting Tree Swallows to climatic perturbations from climate change. Overall, Year 1 of the Tree Swallow Nest Box Project is considered to have been successful based on occupancy at all three parks and a relatively high nest success rate of 80.6%. In comparison, a reported 71% of nests in British Columbia were successful in rearing at least one fledgling. 1 Tree Swallow nest with eggs. Nests are constructed from grasses and lined with loose feathers collected from other species. Dead Tree Swallow nestling approximately two weeks old. Presumed to be a casualty of the heat wave. Summary Tree Swallow nestlings approximately 7 days old. 6 [1] Campbell RW, Dawe NK, McTaggart - Cowan I, Cooper JM, Kaiser GW, McNall MCE, Smith GEJ. 1997. The Birds of British Columbia. Volume 3: Passerines – Flycatchers through Vireos. University of British Columbia Press, Vancouver, BC, Canada. [2] Winkler DW, Hallinger KK, Ardia DR, Robertson RJ, Stutchbury BJ, Cohen RR. 2020. Tree Swallow ( Tachy cineta bicolor ), version 1.0. In: Birds of the World (Poole AF, editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.treswa.01 [3] Government of Canada. 2021. Historical Weather Data. Vancouver Intl A. Available at: https://cl imate.weather.gc.ca/historical_data/search_historic_data_e.html . Accessed: September 2021. [4] Phillip S, Kew SF, Oldenborgh GJ. et al. 2021. Rapid Attribution Analysis of the Extraordinary Heatwave on the Pacific Coast of the US and Canada June 2021. Worl d Weather Attribution. 2021. References 7 Box Number Zone Easting Northing Garden City Lands 1 10U 491499 5447107 2 10U 491456 5447097 3 10U 491426 5447069 4 10U 491401 5447022 5 10U 491364 5446977 6 10U 491329 5446945 7 10U 491302 5446908 8 10U 491280 5446869 9 10U 491283 5446830 10 10U 491320 5446806 11 10U 491332 5446748 12 10U 491314 5446696 13 10U 491276 5446647 14 10U 491241 5446612 15 10U 491214 5446573 16 10U 490985 5446974 17 10U 490966 5447065 18 10U 491011 5447066 19 10U 491010 5447013 20 10U 491030 5446959 Garden City Park 1 10U 491088 5445702 2 10U 490978 5445697 3 10U 491045 5445768 Terra Nova Natural Area 1 10U 485730 5446337 2 10U 485772 5446335 3 10U 485819 5446332 4 10U 485868 5446327 5 10U 485919 5446324 6 10U 485941 5446276 7 10U 485935 5446224 8 10U 485925 5446174 9 10U 485925 5446123 10 10U 485921 5446073 11 10U 485915 5446021 12 10U 485909 5445968 13 10U 485881 5445927 14 10U 485826 5445934 15 10U 485535 5446714 16 10U 485547 5446733 17 10U 485557 5446750 18 10U 485588 5446684 19 10U 485588 5446692 Appendix I: Nest Box Coordinates