HABITAT USE WITHIN and AMONG ROOSTS of CHIMNEY SWIFTS (Chaetura Pelagica)

HABITAT USE WITHIN AND AMONG ROOSTS OF CHIMNEY SWIFTS (Chaetura pelagica)

A Thesis Submitted to the Committee on Graduate Studies in Partial Fulfillment of the Requirements for the Degree of Master of Science in the Faculty of Arts and Science

TRENT UNIVERSITY Peterborough, Ontario, Canada © Copyright by Melanie L. Farquhar 2017 Environmental and Life Sciences Graduate Program December 2017 Abstract

Habitat use within and among roosts of chimney swifts (Chaetura pelagica) Melanie L. Farquhar

Chimney swifts are listed as Threatened nationally and in many provinces within Canada due to rapid population declines. I examined large-scale spatial variation in the maximum size of chimney swift roosts at the northern edge of their range to identify where larger roosts occur. I used multi-sourced data collected across Ontario and Quebec between

1998 and 2013. I found that larger roosts were found at more northerly latitudes, and that very large roosts (>1000 birds) only occurred north of 45°. I also investigated fine-scale patterns of chimney swift positioning inside one of the largest roosts in Ontario. Using digitally recorded images, I calculated the angular position of swifts inside the roost relative to ambient and roost temperature. I found that swifts showed a strong preference for clinging to the south facing wall and clustered more when ambient air temperature was warmer. Thus, huddling in swifts provides additional or alternate benefits, other than serving purely to reduce costs of thermoregulation at low ambient temperatures. This research contributes to the understanding of chimney swift roosting ecology and identifies large roosting sites that should be retained for conservation.

Keywords: anthropogenic habitat, aerial insectivore, cavity roosting, chimney swift,

Chaetura pelagica, communal roosting, conservation, group size, habitat use, huddling, social thermoregulation, species-at-risk

Acknowledgements

This project would not have been possible without the help of so many people along the way. First, I would like to thank my supervisor, Joe Nocera, for his valuable guidance, support, and his meaningful words of encouragement. I am extremely thankful for the passion, dedication, and hard work of Annie Morin at Canadian Nuclear Laboratories

(CNL), for without her, this project would never have existed. I would like to extend my gratitude to several others at CNL who were critical to the success of this project: Jamie

Carr, for all his help with field equipment, permits and construction; Dave Tanner and Al

Taylor, for sacrificing their summer evenings to help count swifts; Stephen Kenny, for his support on the project and ensuring his staff were available to help; Vinnie Gauthier, for happily preparing endless work permits; Don Sheppard, for his commitment to getting the camera installed; John Leblanc, and all the staff at MPF, for supporting the project and accommodating our requests. Sincere thanks to those who provided their expertise in the field and withstood the scorching heat of rooftops with me while attempting to catch swifts: Sarantia Katsaras, Greg Rand, Meghan Beale, and Hazel Wheeler. An additional thank you to Sarah McGuire and Valerie von Zuben for help analyzing many swift roosting images. I would like to acknowledge Bird Studies Canada and Canadian

Wildlife Service for providing chimney swift monitoring data, and to thank all the citizen scientists who volunteered their time to count swifts. Thank you to my committee

iii members, Gary Burness and Erica Nol, for their valuable comments and advice throughout the process. This research would not have been possible without financial and in-kind support from Canadian Nuclear Laboratories, the Natural Sciences and

Engineering Research Council of Canada and the Ontario Ministry of Natural Resources and Forestry. I am exceptionally grateful for my family and my circle of friends, who not only provided their encouragement and support, but were also a source of inspiration through their own personal and academic achievements. And finally, to James, thank you supporting me in more ways than one, and for taking care of the cats during the field season.

Table of Contents

Abstract ...... ii

Acknowledgements ...... iii

Table of Contents ...... v

List of Figures ...... vii

List of Tables ...... x

CHAPTERS:

1. General Introduction ...... 1

Literature cited ...... 8

2. Spatial patterns in roost size of chimney swifts at their northern range edge ...... 12

Abstract ...... 12

Introduction ...... 13

Methods...... 16

a) Chimney swift monitoring data sets ...... 16

b) Statistical analysis ...... 18

Results ...... 19

Discussion ...... 20

Figures and Tables ...... 24

Literature cited ...... 30

3. Fine-scale spatial patterns of chimney swift aggregations inside a roost ...... 35

Abstract ...... 35

Introduction ...... 37

Methods...... 41

a) Study site ...... 41

b) Video and temperature collection...... 41

c) Image analysis ...... 42

d) Statistical analysis ...... 42

Results ...... 44

Discussion ...... 45

Figures and Tables ...... 54

Literature cited ...... 61

4. General Conclusion ...... 66

Literature cited ...... 71

List of Figures

Figure 2.1 Map of chimney swift roosting sites showing maximum size across Ontario and Quebec, Canada (n = 209). Derived from data collected by Bird Studies Canada and

Canadian Wildlife Services between 1998 and 2013. Roosts are defined as a site used by

9 or more swifts...... 24

Figure 2.2 Maximum number of chimney swifts counted at each roost site (n = 209) compared to the latitudinal position of the roost. Roost size is shown on a log-scale for visual representation although raw data were used in analyses. The line represents the relationship between maximum roost size and latitude using a negative binomial regression. Data were collected from across Ontario and Quebec between 1998 and

2013...... 25

Figure 2.3 Maximum number of chimney swifts counted at each roost site (n = 209) compared to the longitudinal position of the roost. Roost size is shown on a log-scale for visual representation although raw data were used in analyses. The negative binomial regression line is shown for the relationship between maximum roost size and longitude.

Data were collected from across Ontario and Quebec between 1998 and 2013...... 26

Figure 2.4 The maximum number of chimney swifts recorded for each roost in Ontario and Quebec by month (May: n = 52; June: n = 40; July: n = 42; August: n = 70;

September: n = 5). Roost size is shown on a log-scale for visual representation although raw data were used in analyses. Boxes represent the quantiles and median and circles fall outside the 95th percentile...... 27

vii

Figure 3.1 Maximum number of chimney swifts recorded inside a single roost each night between 16 May, 2013 and 24 July, 2013 in eastern Ontario. Dashed lines mark A) pre- nesting (16 May – 9 June), B) nesting (10 June – 8 July) and C) post-nesting (9 July – 24

July) periods...... 54

Figure 3.2 Relationship between hourly overnight ambient air temperature at 60m

(recorded at a weather station ~2km away) and the temperature differential (roost temperature – ambient temperature) from 16 May – 24 July, 2013. The relationship is represented by the linear equation y = – 0.80x + 20.28 (R2 = 0.8375, p<0.001) ...... 55

Figure 3.3 Hourly mean angles of orientation (preferred direction) of chimney swifts inside a single roost during A) Pre-nesting period (16 May – 9 June; n = 168), B) Nesting period (10 June – 8 July; n = 232) and C) Post-nesting period (9 July – 24 July; n = 127).

The overall mean angle of orientation for each period is indicated by the arrow...... 56

Figure 3.4 Ambient air temperature at 60m and the variance around the mean angle of orientation for chimney swifts during A) pre-nesting (16 May – 9 June), B) nesting (10

June – 8 July), and C) post-nesting (9 July – 24 July) periods inside a roost in eastern

Ontario in 2013. Swifts are more clustered around the mean angle as the variance approaches 0, and more dispersed as variance approaches a value of 1. Ambient temperature was significant in all time periods...... 57

Figure 3.5 Roost temperature and the variance around the mean angle of orientation for chimney swifts during A) pre-nesting (16 May – 9 June), B) nesting (10 June – 8 July),

viii and C) post-nesting (9 July – 24 July periods inside a roost in eastern Ontario in 2013.

Swifts are more clustered around the mean angle as the variance approaches 0, and more dispersed as variance approaches 1. Roost temperature was significant in the pre-nesting and post-nesting periods...... 58

List of Tables

Table 2.1 Parameter estimates and standard errors (SE) for the predictive variables of chimney swift roost size in Ontario and Quebec between 1998 and 2013 for the global negative binomial regression model (* indicates significance at alpha < 0.05)...... 28

Table 2.2 Parameter estimates and standard errors (SE) for the predictive variables of chimney swift roost size in Ontario and Quebec between 1998 and 2013 for the best fit negative binomial regression model (* indicates significance at α < 0.05)...... 29

Table 3.1 Hourly overnight (23:00 – 5:00) temperatures recorded inside a chimney swift roost at a depth of 5m compared to ambient air temperature at a height of 60m in 2013 for the pre-nesting (16 May – 9 June, n = 168), nesting (10 June – 8 July, n = 232), and post- nesting (9 July – 24 July, n = 127) periods...... 59

Table 3.2 Gamma GLM parameter estimates for the predictive variables of variance around the mean angle of orientation of chimney swifts roosting inside an industrial chimney during the pre-nesting (16 May – 9 June, n = 168), nesting (10 June – 8 July, n =

232), and post-nesting (9 July – 24 July, n = 127) periods in 2013 (* indicates significance at alpha < 0.05)...... 60

CHAPTER 1:

General Introduction

Most wildlife ecological research focuses on areas of natural habitat and the relationships and dynamics within those areas. Scant attention has been paid to wildlife that has adopted anthropogenically-provided surrogate habitats; however, it is precisely this group of species that most directly comes into contact with many forms of human settlement and industry. Traditionally, conservation efforts have focused on protecting undisturbed habitat, and little conservation value has been placed on anthropogenic habitat (McIntyre & Hobbs 1999; Miller & Hobbs 2002). While there is no doubt that human modification of the landscape has a negative effect on many species and protection of natural areas is an important part of biodiversity conservation (Margules &

Pressey 2000), some species that rely on human-altered habitat may face negative consequences if this habitat type is ignored altogether (Davison & Fitzpatrick 2010).

Thus, to conserve biodiversity in all its forms, effective ecosystem management plans should follow an integrated approach that incorporates multiple land uses and varied ownerships (Knight 1999; Miller & Hobbs 2002; Marzluff & Ewing 2008).

The identification of habitat necessary to support and maintain healthy wildlife populations is required for effective conservation strategies. Identifying and protecting the habitat of species that use human-made habitat presents unique challenges, as the needs of both humans and wildlife must be considered. In species that predominantly use human-made structures (e.g., chimneys, barns, bridges), for which a return to their natural/historical habitat is not an immediately feasible option, how do we determine

1 what structures to protect and over what time frame? In such cases, human safety and maintenance costs are legitimate concerns as human-made structures have finite lifespans and face eventual deterioration. Recently, a policy amendment to Canada’s Species at

Risk Act (SARA) posits that anthropogenic structures can be identified as critical habitat if these structures are deemed necessary for the survival or recovery of a listed species

(Government of Canada 2016). However, this anthropogenic habitat should only serve as an interim measure, with a return to natural habitat as the ultimate goal in recovery and management plans (Government of Canada 2016). Knowledge of how a species uses this anthropogenic habitat over multiple spatial and temporal scales is needed to contribute to the designation of critical habitat, which is especially important and urgent for synanthropic species in strong population decline.

A model synanthropic species

Aerially-foraging insectivorous birds of North America are experiencing widespread population declines (Nebel et al. 2010). Among this group, the chimney swift

(Chaetura pelagica; hereafter, swift) has faced the most dramatic declines of the guild as shown by a 95% reduction in the Canadian population over the past 40 years (COSEWIC

2007). Consequently, swifts have been listed as Threatened both nationally and in many provinces. At the time of listing, the estimated breeding population of swifts in Canada was 12000 individuals (COSEWIC 2007). A guild-wide trend in the decline of aerial insectivores suggests changes in food resources may be the common factor limiting these species and contributing to declines (Nocera et al. 2012). While few historical data on insect populations exist, a study of a historical deposit of swift guano provided evidence that the decline in swift populations may be linked to a shift in the type of insects

2 consumed over a 48-year period (Nocera et al. 2012).

Swifts are currently very closely associated with urban and suburban areas and rely almost exclusively on masonry chimneys for both breeding and roosting habitat

(Steeves et al. 2014). Historically, the natural habitat of swifts was old hollow trees, but swifts quickly adopted man-made structures as North America was industrialized and virgin forest became rare (Graves 2004). In fact, the first record of swifts using human- made habitat in North America came as early as 1664 (Graves 2004), and today, reports of swifts using natural habitat are extremely rare due in part to the past destruction of large diameter trees by extensive and intensive logging practices (Zanchetta et al. 2014).

However, declines in swift populations may now be affected by loss of their surrogate anthropogenic habitat (COSEWIC 2007); a decreasing number of chimneys are available to swifts as the modernization of heating systems means fewer masonry chimneys are being constructed. Additionally, existing masonry chimneys are being capped or lined as safety precautions, which renders them unavailable to swifts. The primary recent conservation action for swifts has been the provision of supplementary habitat in the form of wooden towers for swifts to nest in (Kyle & Kyle 2005; Steeves et al. 2014). Despite being used by swifts in the southern United States, these structures have yet to attract a successful breeding pair in Canada (Finity & Nocera 2012; Nocera, pers. comm.), and in

Ontario it may be because the availability of suitable nesting sites is not yet limiting swift populations (Fitzgerald et al. 2014).

While swifts roost communally, they do not breed communally. Generally only one pair of swifts occupies a nesting chimney, inside which they build a cup-shaped nest that is glued to the wall (Fischer 1958). On average, swifts lay 4 or 5 eggs, and incubation

3 and feeding duties are shared by both parents (Fischer 1958). Occasionally, 1 or 2 helpers may join a breeding pair and share incubating and feeding duties (Dexter 1952). Eggs hatch after approximately 19 days and the young may take their first flight 28-30 days after hatching (Fischer 1958). Parents no longer feed the young after they leave the chimney, and once all the young have fledged, family groups may leave the nest chimney to join communal roosts. Swifts are monogamous and exhibit strong nest site fidelity from year to year (Dexter 1969). In comparison, chimneys used for communal roosting may contain hundreds or thousands of swifts when they gather during spring and autumn migration (Steeves et al. 2014). Roost chimneys are also used throughout the nesting season by non-breeding swifts (Dexter 1969).

While recent studies have focused on habitat use at or around nesting sites (e.g.,

Finity & Nocera 2012; Wheeler 2013), few studies have examined the availability or use of roosting sites. Roosting chimneys are often much larger masonry chimneys associated with schools, churches, and industrial buildings (Steeves et al. 2014). Such large masonry chimneys have not been commonly built since 1960, and many existing roost chimneys are nearing the end of their lifespan and/or are in need of repair, modification, or destruction (COSEWIC 2007). Therefore, the availability of suitable roosting structures may be a factor limiting swift populations, or is likely to be a factor in the future. For example, out of 98 roost sites that have been identified in Quebec since 1998, only 38

(39%) were still available to swifts as of 2010 (Rioux et al. 2010). To inform management decisions about the preservation of existing habitat or the possible provision of new habitat, it is necessary to first understand how swifts use and select preferred roost sites.

Communal Roosting

Communal roosting is common in several species of birds (Eiserer 1984;

Beauchamp 1999), bats (Lewis 1995), and primates (Anderson 1998). Although the evolutionary origin of communal roosting is debated, the benefits of roosting as a group must outweigh the costs of roosting alone for those species that do it. Increased foraging efficiency through information exchange (Ward & Zahavi 1973; Caccamise & Morrison

1986; Bijleveld et al. 2010), decreased predation risk (Weatherhead 1983), and a decrease in the cost of thermoregulation (DuPlessis & Williams 1994; DuPlessis et al. 1994) are the primary, not mutually-exclusive, hypotheses for the formation of communal roosts.

The information centre hypothesis proposes that communal roosts are used to communicate knowledge about good foraging areas (Ward & Zahavi 1973); successful foragers provide information about good foraging areas to less successful foragers at the roost. In turn, successful foragers may receive alternate or additional benefits from communal roosting that make it advantageous to travel back to the roost each night

(Richner & Heeb 1995; Bijleveld et al. 2010). One benefit is that communal roosts may provide increased predator protection; the presence of several individuals, both at the roost site and at foraging areas, increases predator detection and reduces one’s chances of being predated through the dilution effect (Weatherhead 1983; Elgar 1989; Finkbeiner et al. 2012). Additionally, the location and physical characteristics of the roost site may also provide protection from predators (Townsend et al. 2009; Lambertucci & Ruggiero 2013)

Finally, there is evidence to suggest that a reduction in the costs of thermoregulation is an important factor driving the occurrence of communal roosts (DuPlessis et al. 1994;

DuPlessis & Williams 1994; McKechnie & Lovegrove 2001; Hatchwell et al. 2009;

Chappell et al. 2016). Roosting with others can reduce the energetic demands associated with thermoregulation in several ways. Groups of roosting birds can raise the local ambient air temperature, thereby decreasing the gradient between body temperature and ambient air temperature resulting in less heat lost to the environment (Walsberg 1990;

Hayes et al. 1992; Willis & Brigham 2007; Paquet et al. 2016). By huddling close together, birds can reduce their surface area to volume ratio and further decrease heat loss

(Vickery & Millar 1984; Canals et al. 1989; Hayes et al. 1992; Boix-Hinzen &

Lovegrove 1998; Gilbert et al. 2010; Burns et al. 2013). Some communally roosting birds may further increase energetic benefits by roosting in cavities or other habitat that provides a favourable microclimate and additional protection from wind and rain

(Buttemer 1985; Walsberg 1996; Cooper 1999; Sedgeley 2001; Douglas et al. 2017).

Moreover, an individual’s position within a roost may determine the degree of anti- predator and energy saving benefits received (Weatherhead 1983; McGowan et al. 2005).

For example, an individual occupying a more central position within the roost would be less susceptible to predation and incur greater thermal benefits than an individual at the periphery.

As an obligate communally roosting species, swifts presumably receive some energetic and/or fitness benefits from communal roosting; however, little is known about swift behaviour inside the roost. A better understanding of why swifts use roosts can help to determine important habitat for conservation and contribute to designing effective supplementary habitat.

OBJECTIVES

In this study, I examined patterns in how swifts use roosting habitat on both large and small spatial scales. First, I investigated maximum roost size in relation to geographical position and human population density at the northern edge of the swift’s range with the objective of identifying sites that support large numbers of swifts (Chapter

2). Next, I explored the positioning of swifts inside one of the largest single roost structures in Canada to determine if roosts are important for facilitating thermoregulatory behaviour (Chapter 3). The results of these two objectives will refine and improve the effectiveness of recovery and management plans for swifts. While little is known about how swifts select and use habitat in general, there has been some recent research on nesting and foraging habitat use (Finity & Nocera 2012; Wheeler 2013; Fitzgerald et al.

2014), but research on roost use is lacking. Because roosting sites may contain large numbers of birds (100s – 1000s), the removal of one of these sites may have severe adverse effects to the population as a whole. The results of this study will allow us to identify areas that are a high priority for conservation, as well as provide information useful for the design and placement of supplementary habitat. By understanding how and why swifts use roosts, it may be possible to construct artificial roost structures that are successfully used as habitat by swifts to supplement areas of low roost availability.

LITERATURE CITED

Anderson, J. R. (1998). Sleep, sleeping sites, and sleep-related activities: Awakening to their significance. American Journal of Primatology, 46(1), 63–75. Beauchamp, G. (1999). The evolution of communal roosting in birds: origin and secondary losses. Behavioral Ecology, 10(6), 675–687. Bijleveld, A. I., Egas, M., van Gils, J. A., & Piersma, T. (2010). Beyond the information centre hypothesis: Communal roosting for information on food, predators, travel companions and mates? Oikos, 119(2), 277–285. Boix-Hinzen, C., & Lovegrove, B. (1998). Circadian metabolic and thermoregulatory patterns of red‐billed woodhoopoes (Phoeniculus purpureus): the influence of huddling. Journal of Zoology, (244), 33–41. Burns, D. J., Ben-Hamo, M., Bauchinger, U., & Pinshow, B. (2013). Huddling house sparrows remain euthermic at night, and conserve body mass. Journal of Avian Biology, 44(2), 198–202. Buttemer, W. A. (1985). Energy relations of winter roost-site utilization by American goldfinches (Carduelis tristis). Oecologia, 68(1), 126–132. Caccamise, D. F., & Morrison, D. W. (1986). Avian communal roosting: implications of diurnal activity centers. The American Naturalist, 128(2), 191-198. Canals, M., Rosenmann, M., & Bozinovic, F. (1989). Energetics and geometry of huddling in small mammals. Journal of Theoretical Biology, 141(2), 181–189. Chappell, M. A., Buttemer, W. A., & Russell, A. F. (2016). Energetics of communal roosting in chestnut-crowned babblers: implications for group dynamics and breeding phenology. The Journal of Experimental Biology, 219(21), 3321–3328. Committee on the Status of Endangered Wildlife in Canada (COSEWIC). (2007). COSEWIC assessment and status report on the Chimney Swift (Chaetura pelagica) in Canada. Ottawa, Ontario, Canada. Cooper, S. (1999). The thermal and energetic significance of cavity roosting in mountain chickadees and juniper titmice. Condor, 101(4), 863–866. Davison, M. A., & Fitzpatrick, J. W. (2010). Role of human-modified habitat in protecting specialist species: A case study in the threatened Florida Scrub-Jay. Biological Conservation, 143(11), 2815–2822. Dexter, R. W. (1952). Extra-parental cooperation in the nesting of Chimney Swifts. The Wilson Bulletin, 64(3), 133–139. Dexter, R. W. (1969). Banding and nesting studies of the Chimney Swift, 1944-1968. The Ohio Journal of Science, 69(4), 193–213.

Douglas, T. K., Cooper, C. E., & Withers, P. C. (2017). Avian torpor or alternative thermoregulatory strategies for overwintering? The Journal of Experimental Biology, 220(7), 1341–1349. DuPlessis, M., Weathers, W., & Koenig, W. (1994). Energetic benefits of communal roosting by acorn woodpeckers during the nonbreeding season. The Condor, 96(3), 631–637. DuPlessis, M., & Williams, J. (1994). Communal cavity roosting in green woodhoopoes: consequences for energy expenditure and the seasonal pattern of mortality. The Auk, 111(2), 292–299. Eiserer, L. A. (1984). Communal Roosting in Birds. Bird Behavior, 5, 61–80. Elgar, M. A. (1989). Predator vigilance and group size in mammals and birds: a critical review of the empirical evidence. Biological Reviews of the Cambridge Philosophical Society, 64(1), 13–33. Finity, L., & Nocera, J. J. (2012). Vocal and visual conspecific cues influence the behavior of Chimney Swifts at provisioned habitat. The Condor, 114(2), 323–328. Finkbeiner, S. D., Briscoe, A. D., & Reed, R. D. (2012). The benefit of being a social butterfly: communal roosting deters predation. Proceedings of the Royal Society B: Biological Sciences, 279(1739), 2769–2776. Fischer, R. B. (1958). The Breeding Biology of the Chimney Swift Chaetura pelagica (Linnaeus). New York State Museum and Science Service bulletin, 368, 1 – 139. Fitzgerald, T. M., van Stam, E., Nocera, J. J., & Badzinski, D. S. (2014). Loss of nesting sites is not a primary factor limiting northern Chimney Swift populations. Population Ecology, (56), 507–512. Gilbert, C., McCafferty, D., Le Maho, Y., Martrette, J.-M., Giroud, S., Blanc, S., & Ancel, A. (2010). One for all and all for one: the energetic benefits of huddling in endotherms. Biological Reviews of the Cambridge Philosophical Society, 85(3), 545–69. Government of Canada. (2016). Policy Regarding the Identification of Anthropogenic Structures as Critical Habitat under the Species at Risk Act [Proposed]. Graves, G. R. (2004). Avian commensals in Colonial America: when did Chaetura pelagica become the Chimney Swift? Archives of Natural History, 31(2), 300–307. Hatchwell, B. J., Sharp, S. P., Simeoni, M., & McGowan, A. (2009). Factors influencing overnight loss of body mass in the communal roosts of a social bird. Functional Ecology, 23, 367–372. Hayes, J. P., Speakman, J. R., & Racey, P. A. (1992). The contributions of local heating and reducing exposed surface area to the energetic benefits of huddling by short- tailed field voles (Microtus agrestis). Physiological Zoology, 65(4), 742–762.

Knight, R. L. (1999). Private lands: The neglected geography. Conservation Biology, 13(2), 223–224. Kyle, P. D., & Kyle, G. Z. (2005). Chimney Swift towers - New habitat for America’s mysterious birds: A construction guide. College Station, TX: Texas A&M University Press. Lambertucci, S. A., & Ruggiero, A. (2013). Cliffs Used as Communal Roosts by Andean Condors Protect the Birds from Weather and Predators. PLoS ONE, 8(6), 1–8. Lewis, S. (1995). Roost fidelity of bats: a review. Journal of Mammalogy, 76(2), 481– 496. Margules, C. R., & Pressey, R. L. (2000). Systematic conservation planning. Nature, 405(6783), 243–253. Marzluff, J. M., & Ewing, K. (2008). Restoration of fragmented landscapes for the conservation of birds: A general framework and specific recommendations for urbanizing landscapes. Urban Ecology: An International Perspective on the Interaction Between Humans and Nature, 9(3), 739–755. McGowan, A., Sharp, S. P., Simeoni, M., & Hatchwell, B. J. (2005). Competing for position in the communal roosts of long-tailed tits. Animal Behaviour, 72(5), 1035– 1043. McIntyre, S., & Hobbs, R. (1999). A framework for conceptualizing human effects on landscapes and its relevance for management and research models. Conservation Biology, 13(6), 1282–1292. McKechnie, A. E., & Lovegrove, B. G. (2001). Thermoregulation and the energetic significance of clustering behavior in the White-backed Mousebird (Colius colius). Physiological and Biochemical Zooloology, 74(2), 238–249. Miller, J. R., & Hobbs, R. J. (2002). Conservation where people live and work. Conservation Biology, 16(2), 330–337. Nebel, S., Mills, A., McCracken, J. D., & Taylor, P. D. (2010). Declines of aerial insectivores in North America follow a geographic gradient. Avian Conservation and Ecology, 5(2). Nocera, J. J., Blais, J. M., Beresford, D. V, Finity, L. K., Grooms, C., Kimpe, L. E., Kyser, K., Michelutti, N., Reudink M.W., Smol, J. P. (2012). Historical pesticide applications coincided with an altered diet of aerially foraging insectivorous chimney swifts. Proceedings of the Royal Society B: Biological Sciences, 279(1740), 3114–20. Paquet, M., Doutrelant, C., Loubon, M., Theron, F., Rat, M., & Covas, R. (2016). Communal roosting, thermoregulatory benefits and breeding group size predictability in cooperatively breeding sociable weavers. Journal of Avian Biology, 47(6), 749–755.

Richner, H., & Heeb, P. (1995). Is the information center hypothesis a flop? Advances in the Study of Behavior, 24, 1–45. Rioux, S., Savard, J., & Shaffer, F. (2010). Effective monitoring: the case of an aerial insectivore, the Chimney Swift. Trends in Ecology and Evolution, 5(2), 10. Sedgeley, J. A. (2001). Quality of cavity microclimate as a factor influencing selection of maternity roosts by a tree-dwelling bat, Chalinolobus tuberculatus, in New Zealand. Journal of Applied Ecology, 38(2), 425–438. Steeves, T. K., Kearney-McGee, S. B., Rubega, M. A., Cink, C. L., & Collins, C. T. (2014). Chimney Swift (Chaetura pelagica). In A. Poole (Ed.), The Birds of North America Online. Ithica, New York, USA: Cornell Lab of Ornithology. Townsend, J. M., Rimmer, C. C., Brocca, J., McFarland, K. P., & Townsend, A. K. (2009). Predation of a wintering migratory songbird by introduced rats: can nocturnal roosting behavior serve as predator avoidance? The Condor, 111(3), 565– 569. Vickery, W., & Millar, J. (1984). The energetics of huddling by endotherms. Oikos, 43, 88–93. Walsberg, G. E. (1990). Communal roosting in a very small bird: consequences for the thermal and respiratory gas environments. Condor, 92(3), 795–798. Walsberg, G. E. (1996). Thermal consequences of roost-site selection: The relative importance of three modes of heat conservation. The Auk, 103(1), 1–7. Ward, P., & Zahavi, A. (1973). The importance of certain assemblages of birds as “information-centres” for food finding. Ibis, 115(4), 517–534. Weatherhead, P. (1983). Two principal strategies