Swallows (Family Hirundinidae) and Swifts (Family Apodidae) forage for insects on the wing. Their aerial proficiency can be observed on any summer day, as they dart and dash over open fields, skim along the surface of water bodies, or soar above forest canopies. While the members of these two families are often observed by even the most casual observer, they are regularly missed during formal bird surveys designed to estimate density. For example, of the 104 articles contained in the monograph Estimating Numbers of Terrestrial Birds (Ralph and Scott 1981), only two articles contain information about swallows and swifts, both of which use data of relative density obtained through the North American Breeding Bird Survey (BBS) (Robbins 1981; Robbins and Stallcup 1981). The reason for this discrepancy is that traditional surveys such as spot mapping, line transects, or point counts have been designed to take advantage of the behaviour of birds, which, in general, defend an all purpose (relatively small) territory, solicit for mates by singing from a branch (or other suitable structure), and are not colonial (Erskine 1981). Swallows and swifts do not exhibit these behaviours, thus they are not suitable for surveying with these methods.
The swallows and swifts which breed in British Columbia are migratory. The early migrants such as the Tree Swallow or the Violet-green Swallow, return to the province in late February, while the later migrants such as the Barn Swallow and Black Swift, usually make their first appearance in mid to late May (Cannings et al. 1987; Campbell et al. 1990). All of the species belong to the same foraging guild, aerial pursuers of aerial insects (Ehrlich et al. 1988).
This manual recommends methods and outlines protocol for standardizing data collection procedures for swallows and swifts. This is an important group to monitor because they often forage in areas of potential high pollution (river and estuaries) and high pesticide use (agricultural lands).