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The Eastern Phoebe (Sayornis phoebe) is a common inhabitant of Southern Ontario. The 2nd edition of the Ontario Breeding Bird Atlas shows that peak abundance in the province aligns with the southern edge of the Canadian Shield. In these areas, the high forest coverage and availability of nest sites (e.g. cottages, bridges and other man-made structures) likely contribute to higher densities (Cadman et.al. 2007). It has been suggested that the species underwent a marked range expansion and population increase in unison with early development and human settlement, which greatly increased the availability of suitable nest sites (Weeks, H.P., Jr. 1994). Phoebes attach their nests directly to a vertically sloped surface, which provides overhead protection from the elements, in much the same manner as Barn Swallows (Hirundo rustica). Man-made structures such as bridges, culverts and eaves of buildings are just a few of many ‘unnatural’ features suitable for the species. What does this suggest for precolonial status of the Eastern Phoebe in Ontario? The nest pictured above was found last week and its location illustrates this question.
The Eastern Phoebe has been a resident of Ontario’s woodlands since long before axe-wielding Europeans arrived. This particular nest was attached directly to a vertical rock wall below a cut in the rock. These rock formations occur throughout the FBS study area – in forest interiors, dry rock barrens and edges of lakes and ponds. It is plausible that the high numbers detected along the southern edge of the shield are also attributable to the proliferation of these naturally occurring nest sites. Click here for more info on nesting Eastern Phoebes in the Frontenac Arch.
In Canada, the Louisiana Waterthrush (Seirus motacilla) has a small range limited to southern Ontario and Quebec. The population is small, estimated at <200 pairs, and restricted to mature forested ravines with clear, gravel-bottomed streams and/or woodland swamps. Louisianas are considered “area sensitive”. According to a Maryland study (Robbins 1979) a minimum of 100 contiguous hectares of mature habitat is needed for successful breeding (McCracken 2006). In Ontario, the Louisiana Waterthrush is a rare but regular breeder in southwestern Ontario. Smaller numbers also occur in deeply incised valleys of the Frontenac Arch where mature forest is present.
The Frontenac Arch sits at the northern limit of the continental breeding range for Louisiana Waterthrush. Here, annual occupancy and productivity of breeding sites are probably influenced by weather cycles and periodic expansion/contraction of the source population further south, possibly upstate New York. It is suggested that north wandering immigrants cause a “rescue effect” for the Canadian population. There is also evidence of the species expanding its range northward, likely in response to maturing second growth forest cover. Climate change, beavers and water quality are also important influences on the status of the species in the Frontenac Arch.
We have started an inventory of Louisianas in Frontenac Provincial Park and in accessible habitats immediately surrounding the park. Louisianas will breed in woodland swamps and along clean creeks and streams, both of which occur in abundance in these areas. Potential nest sites have been identified from several sources and will be surveyed in May 2010 to determine occupancy and breeding status. This information will improve our knowledge of the local population’s size, demography and habitat preferences. The work will also enable monitoring through comparative analysis in future years.