STATUS OF BARN SWALLOWS (Hirundo rustica erythrogaster)
AND CLIFF SWALLOWS (Petrochelidon pyrrhonota) IN
THE LITTLE CAMPBELL WATERSHED
A ROCHA CANADA CONSERVATION SCIENCE SERIES
August 2014
AUTHORS:
Hannah F. R. Hereward, A Rocha Canada Christy Juteau, A Rocha Canada Andrew Baylis, A Rocha Canada
CONTACT: [email protected]
STATUS OF BARN SWALLOWS (Hirundo rustica erythrogaster) AND CLIFF SWALLOWS (Petrochelidon pyrrhonota) IN THE LITTLE CAMPBELL WATERSHED Aug 2014| i
Executive Summary
Swallows (Hirundinidae) are a group of migratory bird species found across the world. Barn Swallows (Hirundo rustica erythrogaster) and Cliff Swallows (Petrochelidon pyrrhonota) both migrate to North America annually for the breeding season. Populations of both species have declined over the last 40 years. The purpose of this study was to begin a local monitoring programme for Barn and Cliff Swallows within the Little Campbell River watershed (LCRW), British Columbia, Canada. Barn Swallow nests were monitored at nine sites throughout the LCRW. One Cliff Swallow colony was monitored at A Rocha’s Brooksdale Environmental Centre between April and August 2014. Cliff Swallow banding took place twice within the breeding season. We banded 30 Cliff Swallows (20 birds on June 29 and 10 on July 12, 2014). The arrival and departure dates of both species were documented at each site. We analyzed the effect of surrounding land cover within 400 m of each site on the number of Barn Swallow chicks fledged. Old Barn Swallow nests were present at all nine sites but only five sites contained active nests. In total, we monitored 25 active and 39 inactive Barn Swallow nests and 11 inactive and 47 active Cliff Swallow nests. Amount of pasture within 400 m of the nest site was positively associated with the number of
Barn Swallow chicks fledged per site (rs = 0.718, p = 0.019). While our results suggest a dependence on pastures and open fields for Barn Swallow nesting success, further annual studies are needed to determine the status of Barn and Cliff Swallow populations within the Little Campbell River watershed.
STATUS OF BARN SWALLOWS (Hirundo rustica erythrogaster) AND CLIFF SWALLOWS (Petrochelidon pyrrhonota) IN THE LITTLE CAMPBELL WATERSHED Aug 2014| ii
Acknowledgements
We would like to thank all the land-owners who allowed us to check nests on their properties weekly. Also we would like to thank Campbell Valley Park for allowing us to access the park and buildings throughout the season. Thank you to Andrew Baylis and Rebecca Hannigan for aiding in fieldwork.
Recommended Citation:
Hereward, H., F., R., Juteau, C., and Baylis, A. 2014. Status of Barn Swallows and Cliff Swallows in the Little Campbell River watershed. A Rocha Canada Conservation Science Series. A Rocha Canada, Surrey, B.C., Canada.
Cover illustrations:
From left to right: Barn Swallow (Hirundo rustica erythrogaster) building a nest, Little Campbell Hatchery and Semiahmoo Fish and Game Club, Cliff Swallow (Petrochelidon pyrrhonota) in the hand during banding, A Rocha Brooksdale. All rights reserved.
Content (excluding the illustrations) may be used without permission, with appropriate credit to the source.
STATUS OF BARN SWALLOWS (Hirundo rustica erythrogaster) AND CLIFF SWALLOWS (Petrochelidon pyrrhonota) IN THE LITTLE CAMPBELL WATERSHED Aug 2014| iii
Table of Contents Executive Summary ...... ii
Acknowledgements ...... iii
Table of Contents ...... iv
Introduction ...... 5
Cliff Swallows ...... 5 Barn Swallows ...... 6 Methods ...... 8
Barn Swallow Site Selection ...... 8 Cliff Swallow Site Selection ...... 8 Site Assessment...... 10 Nest Monitoring ...... 10 Analysis ...... 10 Results ...... 11
Cliff Swallow Nesting Activity and Banding ...... 11 Barn Swallow Nesting Activity ...... 11 Land Cover ...... 12 Discussion ...... 27
Breeding Phenology ...... 27 Nest Success ...... 28 Land Cover ...... 29 Further Study ...... 29 References ...... 29
STATUS OF BARN SWALLOWS (Hirundo rustica erythrogaster) AND CLIFF SWALLOWS (Petrochelidon pyrrhonota) IN THE LITTLE CAMPBELL WATERSHED Aug 2014| iv
Introduction Swallows (Hirundinidae) are a group of migratory bird species found across the world (Turner, 2006). Six out of 18 swallow genera are found in western North America: Tachycineta, Stelgidopteryx, Riparia, Hirundo, Petrochelidon and Progne (Sibley, 2003; Sheldon et al., 2005; Dor et al., 2010).
Cliff Swallows The Petrochelidon genus is split into 9 species (Sheldon et al., 2005). The Cliff Swallow (Petrochelidon pyrrhonota, previously Hirundo pyrrhonota) (Fig. 1) migrates between South America and North America, breeding in North America between May and July (Grant and Quay, 1977). Since 2000, Bunnell (unpublished data, 2014) has observed Cliff Swallow clutches in British Columbia as early as April 28, with 54% of first clutches occurring in June. Both parents assist in the nest building, incubating and rearing of 1 to 2 broods of chicks per year (Smith et al., 2005).
Figure 1. Cliff Swallow (Petrochelidon pyrrhonota) and nests. Source: H Hereward, 2014.
Cliff Swallows typically nest under large bridges and on buildings in close association with human habitation, but prior to extensive human habitation they nested on cliff and rock edges (Gorenzel and Salmon, 1982). Cliff Swallows nest in colonies containing 2 to over 3,700 nests (Brown, Brown and Danchin, 2000). Their nests are created from mud globules joined together to form an upside-down dome with an entrance tunnel (Samuel, 1971).
The IUCN (International Union for the Conservation of Nature) categorises Cliff Swallows as ‘least concern’ and states that their populations are increasing (BirdLife International, 2012). Furthermore, the 2010 Wild Species report stated that Cliff Swallow populations are ‘secure’, meaning they remain widespread or abundant (Canadian Endangered Species Conservation Council, 2011). The 2011 Breeding Bird Atlas Survey in Canada demonstrates that although Cliff Swallows are widespread, they have declined within Canada by 50% over the last 40 years (Environment Canada, 2014). The reasons for this decline are currently unknown, but may be due to a decrease in insect abundance (their primary food source) and an increase in House Sparrows (Passer domesticus), which are known to take over Cliff Swallow nests (Leasure, Kannan and James, 2010; Nebel et al., 2010).
STATUS OF BARN (Hirundo rustica erythrogaster) AND CLIFF SWALLOWS (Petrochelidon pyrrhonota) IN THE LITTLE CAMPBELL WATERSHED Aug 2014| 5
Barn Swallows Barn Swallows (Hirundo rustica) are comprised of 6 subspecies (Dor et al., 2010). The H. r. rustica subspecies ranges between Europe and North Africa. Two subspecies are distributed within Africa and the Middle East (savignii and transitiva). There are two Asian subspecies (tytleri and gutturalis) and one subspecies that breeds in North America (erythrogaster) (Fig. 2).
Figure 2. Barn Swallow (Hirundo rustica erythrogaster) and nest. Source: H Hereward, 2014.
Hirundo rustica erythrogaster breeds as far north as southern Alaska and as far south as Mexico. They annually migrate from South America, remaining on their breeding grounds from May through early September (Turner, 2006; Stotz, 1992). Bunnell (unpublished data, 2014) found that the time Barn Swallows spent at their breeding sites in British Columbia increased by two weeks between the 1960s and 1990s.
Like Cliff Swallows, Barn Swallows (hereafter referring to H. r. erythrogaster) construct nests from mud globules; however, they also use straw and grass as nest materials and line the inside of nests with feathers (COSEWIC, 2011). In addition, Barn Swallow nests are generally attached to something vertical (e.g., the side of a beam) and are a half-cup shape. Barn Swallow nests are usually built at least 2 m from surrounding nests (COSWIC, 2011).
Despite historically nesting along cliffs, caves and other natural structures, recently most reported Barn Swallow nests have been found on artificial structures (Speich, Jones and Benedict, 1986; Zink et al., 2006; Redmond and Murphy, 2007). With an increase in human settlement and building structures, Barn Swallow populations have expanded in areas that previously would have had low numbers (Zink et al., 2006). However, Barn Swallow populations have declined by 80% in Canada and 87% in BC over the last 40 years (Environment Canada, 2014). According to the North American Breeding Bird Survey, Barn and Cliff Swallows declined between 1966 and 2012 in North America. This trend was STATUS OF BARN (Hirundo rustica erythrogaster) AND CLIFF SWALLOWS (Petrochelidon pyrrhonota) IN THE LITTLE CAMPBELL WATERSHED Aug 2014| 6 significant for Barn Swallows (p < 0.05) but not for Cliff Swallows (Sauer et al., 2013). Both species also declined between 2002 and 2012, although the rate of decline slowed (p < 0.05 for Barn Swallows, p < 0.1 for Cliff Swallows; Sauer et al., 2013; Figs. 3 and 4). The reasons for these declines are unclear but are likely associated with concurrent declines in the swallows’ insect prey (Nebel et al., 2010).
Figure 3. Cliff Swallow (Petrochelidon pyrrhonota) population decline. Index is defined here as the estimated average abundance of Cliff Swallows on the Breeding Bird Survey routes, estimated for a given year by an average observer. Source: Environment Canada, 2014.
Figure 4. Barn Swallow (Hirundo rustica erythrogaster) population decline. Index is defined here as the estimated average abundance of Barn Swallows on the Breeding Bird Survey routes, estimated for a given year by an average observer Source: Environment Canada, 2014.
STATUS OF BARN (Hirundo rustica erythrogaster) AND CLIFF SWALLOWS (Petrochelidon pyrrhonota) IN THE LITTLE CAMPBELL WATERSHED Aug 2014| 7
The purpose of this study was to begin a local monitoring programme for both species within the Little Campbell River watershed (LCRW) in British Columbia. At nine sites containing active or historic Barn Swallow nests, we documented the arrival and departure dates of Barn Swallows and counted the number of eggs laid, chicks hatched and chicks fledged for each active nest. We analyzed the effects of surrounding land cover within 400 m of each Barn Swallow nest site on the number of chicks fledged. We also monitored an active Cliff Swallow colony at A Rocha’s Brooksdale Environmental Centre and banded Cliff Swallows twice within the breeding season.
Methods
Barn Swallow Site Selection We originally selected 10 sites thought to contain Barn Swallow nests within the Little Campbell River watershed (LCRW; Fig. 5). The LCRW extends across three municipalities within British Columbia: the Township of Langley, City of Surrey and City of White Rock, and also extends into the U.S. state of Washington. The LCRW is 75 km2, with a mixture of urban housing, agricultural land and deciduous and coniferous woodland. Sites were selected based on the known presence of active or old Barn Swallow nests or reported Barn Swallow activity. Sites were surrounded by a variety of habitat types and were located on both private properties and regional parkland. All sites contained one or more buildings or structures that could be used by nesting Barn Swallows, such as bridges, barns or sheds. After conducting a thorough search for Barn Swallow nests at each site, one site was eliminated (White Rock Footbridge) due to the absence of any nests despite the presence of foraging swallows.
Cliff Swallow Site Selection One site was selected from within the LCRW for Cliff Swallow monitoring (Brooksdale; Fig. 5). This site was selected based on the known presence of active Cliff Swallow nests located on both ends of a heritage barn at A Rocha Canada’s Brooksdale Environmental Centre.
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Figure 5. Locations of the original 10 sites searched for Barn Swallow nests (labelled from east to west in the legend) including one Cliff Swallow site (Brooksdale – light green). One site contained no Barn Swallow nests (White Rock Footbridge – light blue). Source: H Hereward, 2014.
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Site Assessment Preliminary visits were conducted at each site to confirm the presence of breeding Barn and/or Cliff Swallows. At each site all possible nesting areas, including eves and beams around/in houses, barns, sheds etc., were searched for swallow nests. Numbers of individual Barn and/or Cliff Swallows were recorded alongside any active or old Barn and/or Cliff Swallow nests. The location of each site was recorded using a handheld GPS. In-tact nests were numbered and mapped.
Nest Monitoring
Each site was visited once a week from April 11 to August 20, 2014, between 08:00 and 12:30. A camera attached to a pole was used to count and record the number of eggs and/or chicks (live or dead) in each nest. The weather, temperature, and number of foraging swallows in the vicinity of the nest were also noted.
Because the Cliff Swallow nests were located too high for the camera to reach, only observations of movements in and out of the nests were recorded (for 10 minutes per nest), alongside the weather, temperature, number of foraging swallows in the vicinity and observers. Cliff Swallow banding took place twice within the breeding season (June 29 and July 12, 2014) and was conducted by Vancouver Avian Research Centre. This was achieved by erecting a mist net on a pulley system attached to the top of the barn roof in order to catch the Cliff Swallows that were going in and out of their nests.
Analysis The number of active Barn and Cliff Swallow nests was calculated across the breeding season. The number of successfully fledged Barn Swallow chicks was calculated for each brood and nest and summed across each site (n = 10). We included the White Rock Footbridge in this analysis, even though this site contained no Barn Swallow nests. We drew 400-m radius buffers around each site and calculated the percent cover of each of five land cover types within each buffer. This was conducted using ArcGIS and a pre-existing classified land cover layer (NAIP orthophoto mosaic for Columbia County, Washington; Montgomery, 2009). A 400-m radius was chosen because it falls between the Barn Swallow home range sizes described by Bryant and Turner (1982) (170 m) and Samuel (1971) (800 m). The 400-m radius buffer also coincided with the distance Barn Swallows were observed foraging from their nests during this study. We used a Spearman Rank Correlation test to analyze the effect of land cover type on the total number of fledged Barn Swallow chicks at each site using Minitab17.
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Results
Cliff Swallow Nesting Activity and Banding The only Cliff Swallow colony observed in this study was located at Brooksdale Environmental Centre. The Cliff Swallows arrived at Brooksdale on April 11, 2014. Cliff Swallow nesting activity peaked at the beginning of July, with a total of 58 nests and 47 active nests on July 2.
Cliff Swallow banding took place on June 29 and July 12, 2014. On June 29 we caught and banded 20 birds (2 hatch-year and 18 after hatch-year). On July 12 we caught and banded 10 birds, including one recapture (all after hatch-year).
Barn Swallow Nesting Activity Across the nine active Barn Swallow sites, the first observed Barn Swallows arrived at the Hatchery on April 24, 2014. In total there were 19 successful first broods. First eggs were observed at the Hatchery on May 30, 2014. There were 12 successful second broods; first eggs from second broods were observed in Nathan’s Barn on July 2, 2014 (Fig. 6).
12
10
8 1st Brood Building 1st Brood Eggs 6 1st Brood Chicks 2nd Brood Building
Number of Nests 4 2nd Brood Eggs 2nd Brood Chicks 2
0 01-May 21-May 10-Jun 30-Jun 20-Jul 09-Aug
Figure 6. Number of Barn Swallow nests and stages of nesting activity across 9 sites throughout the Little Campbell watershed in 2014.
Five sites contained both active and inactive Barn Swallow nests during the breeding season, and four sites contained only inactive nests (Fig. 7). In total, we monitored 25 active and 39 inactive Barn Swallow nests across all sites. Nathan’s Barn contained the most active nests (9) followed by the Chicken Farm (7). Brooksdale and the Campbell Valley Park Main Office contained the fewest active nests (2). Campbell Valley Park’s Equestrian Centre contained the most inactive nests (12) but had no active nests.
STATUS OF BARN (Hirundo rustica erythrogaster) AND CLIFF SWALLOWS (Petrochelidon pyrrhonota) IN THE LITTLE CAMPBELL WATERSHED Aug 2014| 11
14
12
10
8
6
Number of Nests 4
2 not active
0 active
Feedlot Hatchery Brooksdale Nathan's Barn
White Rock Footbridge Robertson's Chicken Farm Campbell Valley Park - Rowlatt Campbell Valley Park - Main Office Campbell Valley Park - Lochiel School Campbell Valley Park - Equestrian Centre
Figure 7. Number of active and inactive Barn Swallow nests at each site across the Little Campbell River watershed, BC.
Nathan’s Barn had the greatest number of successfully fledged chicks (28 from first clutches and 9 from second clutches; Fig. 8, Table 1). At Campbell Valley Park’s Main Office, only 3 chicks fledged, all from a second clutch (Figure 8, Table 1).
30 Fledglings from 1st Clutch 25 Fledglings from 2nd Clutch
20
15
10
5 Total ofnumber fledged chicks per site
0 Hatchery Nathan's Barn Brooksdale Campbell Valley Robertson's Park - Main Office Chicken Farm
Figure 8. The number of Barn Swallow chicks fledged for the first and second clutches at each site containing at least one active nest.
Land Cover Five different land cover types surrounding the sites within a 400-m radius buffer were identified (forest, fresh water/marsh, marine/marsh, grass/pasture, and urban; Figs. 9 and 10). Forest, grass/pasture, and urban were the most prominent habitat types. Nathan’s Barn and the
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Hatchery had the greatest amount of surrounding grass/pasture within 400 m (72% and 70%, respectively) and the highest total number of chicks fledged (28 and 18, respectively; Table 1). The 5 sites where no chicks fledged had the smallest amount of surrounding grass/pasture (Table 1).
Robertson's Chicken Farm Campbell Valley Park - Main Office Campbell Valley Park - Lochiel School Campbell Valley Park - Rowlatt Campbell Valley Park - Equestrian Centre Brooksdale Nathan's Barn Hatchery Feedlot White Rock Footbridge
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Forest Fresh water/marsh Marine/marsh Grass/Pasture Urban
Figure 9. Percent cover of land cover types within a 400-m radius buffer surrounding each Barn Swallow nest site within the Little Campbell River watershed, BC.
Table 1. Number of Barn Swallow chicks fledged and percentage of grass/pasture within a 400-m radius buffer at each site. Site Total number Grass/pasture (%) chicks fledged Campbell Valley Park - Equestrian 0 46 Centre Campbell Valley Park - Lochiel School 0 45 Campbell Valley Park - Rowlatt 0 30 Feedlot 0 41 White Rock Footbridge 0 13 Campbell Valley Park - Main Office 3 52 Brooksdale 14 39 Hatchery 18 70 Robertson's Chicken Farm 20 49 Nathan's Barn 37 72
The number of Barn Swallow chicks fledged per site was positively correlated with amount of grass/pasture within a 400-m radius buffer surrounding each site (Spearman Rank Correlation; rs = 0.718, n = 10, p = 0.02; Table 2, Fig. 11).
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Figure 10. Land cover types surrounding each Barn Swallow nest site (labelled from east to west in the legend) with a 400-m radius buffer within the Little Campbell River watershed, BC. Inset shows an enlargement of the buffer surrounding the White Rock Footbridge. The White Rock Footbridge contained no Barn Swallow nests, while all other sites contained at least one nest.
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Table 2. Spearman Rank Correlation Coefficient (rs) and p-value for associations between number of Barn Swallow chicks fledged per site and percentage of each land cover type within a 400-m radius buffer (n = 10).
Land cover type rs value p-value Grass/Pasture 0.71 0.019 Forest -0.59 0.074 Fresh water/marsh -0.35 0.328 Marine/marsh 0.33 0.328 Urban -0.07 0.858
80% 70% 60% 50% 40% (rs=0.718, n=10, P=0.019) 30%
Grass/pasture (%) 20% 10% 0% 0 5 10 15 20 25 30 35 40 Total number of chicks fledged
Figure 11. Relationship between the number of Barn Swallow chicks fledged at each site (n = 10) within the Little Campbell River watershed and percentage of grass/pasture within a 400-m radius buffer surrounding each site.
Discussion
Breeding Phenology Barn Swallow individuals in the Little Campbell River watershed arrived within the range of dates reported by Bunnell (unpublished data, 2014) and were beginning to nest by the end of April 2014. Bunnell (unpublished data, 2014) reported that Barn Swallows arrived earlier (around April 14) in the 1990s compared to the 1960s (around April 27). He also noted Cliff Swallows having clutches as early as April 28 prior to 2000, with 54% of nesting occurring between June 8 and 28. During this study, some Cliff Swallow nests were already occupied STATUS OF BARN (Hirundo rustica erythrogaster) AND CLIFF SWALLOWS (Petrochelidon pyrrhonota) IN THE LITTLE CAMPBELL WATERSHED Aug 2014| 27 at Brooksdale by April 22. The Cliff Swallow population peaked at the beginning of July, with a total of 58 nests and 47 active nests on July 2. Continued annual monitoring will be used in future years to document arrival dates for Barn and Cliff Swallows and to clarify whether these species are arriving into their breeding grounds earlier than previously recorded.
Nest Success In this study, 25 active and 39 inactive Barn Swallow nests were monitored across the LCRW. Nests ranged from 2-5 years old, with some possibly older than this. The high number of inactive versus active nests in sites with old Barn Swallow activity was surprising, but we were not able to discern whether the population is declining using our data alone and longer-term monitoring is necessary. A hematophagous mite infestation may explain the presence of so many inactive nests (Barclay, 1988; COSEWIC, 2011). However, while this may explain why there are some inactive nests at sites where other nests are active, it does not explain why a site would be completely inactive (such as Campbell Valley Park Equestrian Centre) (COSEWIC, 2011).
This study confirms that the number of Barn Swallow chicks per clutch is generally higher in the first clutch compared to the second (COSEWIC, 2011). This could be due to competition for food in sites with a higher concentration of nests (COSEWIC, 2011). The latter may explain the lower chick count for second clutches at Nathan’s barn, which had the highest concentration of nests. Nathan’s barn is surrounded by pasture and is grazed by cows on a rotation. The cows were moved farther away from the site by mid-summer, which could have caused a decline in insect availability and resulted in fewer second brood chicks fledging (Ambrosini et al., 2002; COSEWIC, 2011).
During the field season, two chicks were found dead out of their nests and three nests completely failed (all chicks died). One chick fatality and one failed nest occurred at the Hatchery. This nest failure was a late pair to arrive and only attempted one brood. The chicks were around halfway to fledging when they died. One of the chicks found out of its nest was at the Hatchery and appeared to have fallen out the nest; possibly prematurely fledged. A second nest failure occurred at Nathan’s barn. The chicks in this nest appeared ready to fledge, but the following week they were found dead in the nest. It is uncertain why these chicks didn’t survive. The final nest failure and chick death both occurred at the Campbell Valley Park Main Office. A young chick with little feather growth was found dead below one of the two active nests at the site (the other chicks in that nest survived). The
STATUS OF BARN (Hirundo rustica erythrogaster) AND CLIFF SWALLOWS (Petrochelidon pyrrhonota) IN THE LITTLE CAMPBELL WATERSHED Aug 2014| 28 other active nest at the site completely failed. These chicks were found dead, hanging from the nest and on the ground below the nest. The cause of this nest failure is unknown.
Land Cover The positive correlation between amount of grass/pasture and the number of fledged chicks per site coincides with other studies that have found Barn Swallows to be associated with pasture (Ambrosini et al., 2002). This is not surprising as pasture provides suitable materials for building nests as well as foraging ground for insects (Bryant and Turner, 1982; Ambrosini et al., 2002).
Further Study Further studies could assess Barn Swallow chick survival rates by monitoring the nest sites more frequently, providing more detailed records of egg-laying dates and project expected hatching days. Banding the Barn Swallow chicks would also aid in further data collection and monitoring. It would be beneficial to continue annual monitoring of the Cliff Swallow colony, including banding 2-3 times throughout the breeding season to gain further information and insight into the biology and ecology of these Cliff Swallows. For both species, it would be useful to study the distance they travel to forage and whether this changes throughout the breeding season. Finally, it would be beneficial to increase the number of Barn Swallow nest sites monitored throughout the LCRW in order to increase the power of statistical tests and more fully understand their breeding biology in this region.
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