Tree Swallows

Tree Swallows are a common sight nesting in boxes on fence posts throughout Beaver County and elsewhere. These beautiful glossy blue and white birds are agile and dynamic flyers—which they have to be to catch the flying insects on the wing that they need to feed themselves and their young.

  • Since 1984, BBO has maintained and monitored Tree Swallow nest boxes along the 'shoreline' of Beaverhill Lake
  • Currently two grids of boxes on the south shore and one row along ‘Rowan’s Route’ (Township Road 510) are monitored
  • Basic monitoring of these boxes is conducted at least once per week and ideally twice per week from first egg laying to last fledging, and includes banding all young and as many adults as possible


Approximately the size of a dime, geo-locators are light data loggers that record light levels and time of day. From these data, latitude and longitude can be determined which can then be used to derive migratory routes. These devices are non-transmitting; so to obtain the recorded data the data logger needs to be retrieved.

  • Their accuracy is of approximately ±150 km, and they can have a battery life of several years
  • In 2013 Geoff Holroyd and Helen Trefry attached geolocators on 40 adults. In 2014, 13 of 40 geolocators were recovered and 30 more geolocators were attached. The field work portion of study concluded in 2015 when an additional 13 geolocators were recovered
  • The geolocators showed that BBO’s Tree Swallows migrated first to the Dakotas and remained there for about two months where they presumably molted
  • Then the swallows migrated down the Mississippi Valley to winter around the Gulf of Mexico and Caribbean from Florida to Mississippi to Veracruz, Mexico, Yucatan and one to Honduras