BARN SWALLOW (HIRUNDO RUSTICA) NESTING HABITAT, USE OF BRIDGES AND CULVERTS AND OTHER STRUCTURES, AND IMPLICATIONS TO INFRASTRUCTURE PROJECTS IN ONTARIO

摘要

Barn Swallow is a medium-sized song bird that is approximately 15 to 18 cm long, which feeds on flying insects. They are easily recognized by their blue glossy back and upper wings, rusty- orange forehead and throat, brownish underbelly, and their deeply forked tails. In Ontario, they are most common in southern and central Ontario but occur as far north as Hudson Bay (COSSARO 2011). Barn Swallows nest on walls or ledges of barns and on other human-made structures such as bridges, culverts or other buildings (Lepage 2007). Barn Swallow often nest in small colonies of 2 to 59 nests in Ontario (Peck and James 1987), and often nest together with Cliff Swallows. Barns Swallows feed on aerial insects while foraging in open habitats such as meadows, hay, pasture or even mowed lawn. (COSEWIC 2011). Barn Swallows are associated with grassland. They will also frequently forage in woodland clearings, over wetland habitats or open water where insect prey are abundant. A review of historical data from the Ontario Nest Records Scheme was conducted by Bird Studies Canada and Stantec (Richardson et al. 2015) to identify historic patterns in use of structures. This analysis showed that although barns are the most commonly used nesting structure, their use over time has decreased, whereas the use of bridges and culverts has increased. To investigate present day use of structures, more than 500 bridges and culverts were surveyed from 2010-2015. The objective was to determine if there was a relationship between the presence of Barn Swallow nests and the physical characteristics of bridges and culverts, and the surrounding landscape. Preliminary analyses showed that only about 20% of bridges and culverts surveyed were used by Barn Swallows, although this varied across the province (Richardson et al. 2015) Barn Swallows appeared to select concrete culverts that were greater than 1.5 m wide; while unused culverts tended to be smaller in size or made of metal materials (Richardson et al. 2015). The surrounding landscape may also be an important contributor to the presence of nesting Barn Swallows; their distribution in Ontario appears to be related to the availability of open country habitat and possibly also to cattle abundance (Richardson et al. 2015).