The Saugeen/Bruce Peninsula is the largest intact natural habitat remaining in southern Ontario and it is an important flyway for migrating birds. The peninsula possesses diverse and unique ecosystems including globally rare alvar and cliff ecosystems, an extensive array of flora including 44 species of orchids, 50 species of ferns and several endemic species, and the oldest trees in eastern North America.
At the 2010 Sources of Knowledge Forum, Rod Steinacher, then President of the Bruce Peninsula Bird Observatory (BPBO), gave a presentation on the Patterns in Migration of Passerines through the Cabot Head Area. A ‘passerine’ is a general name for perching land birds and one of the primary functions of the BPBO at the Cabot Head Research Station is to observe their migration patterns. Mr. Steinacher said that over a five year period, the spring migration is organized by sex and age, unlike the fall migration. Apparently, these two patterns, as opposed to the arrival dates of birds to the area that are dependant on environmental factors, such as day to day weather conditions, can be predicted with some precision.
The Bird Observatory research station at Cabot Head is now in its 19th year of migration monitoring. Passerines, which obviously try to limit their flight time over open water, are “funnelled” by the Saugeen/Bruce Peninsula as they move north, making Cabot Head the ideal location for a bird observatory to monitor the number of migrating birds. In 2002, the Cabot Head area was declared an international “Important Bird Area” (IBA) because of the globally significant portion of the Red-necked Grebe population that use the area in spring and fall as a staging area during their migration. Only a few locations on the Great Lakes serve this function, as the grebes move back and forth between their wintering grounds on the Atlantic coast and their breeding ground in the north central and north western parts of the continent.
The observatory publishes an annual spring and fall migration report summarizing the field work on their excellent website. For example in spring 2018, a total of 160 species were detected during the monitoring period. A complete list of all species observed, with season estimated totals, days with observation, maximum and minimum daily totals, is provided in the report’s appendix. In the spring of 2018, a total of 1159 birds of 67 species were banded and 52 birds of 15 species were recaptured. In the fall, a total of 141 species of birds were detected in the standard count area over the course of the field season. Among them, 76 species have been seen every fall. Most species are seen on a few occasions only (less than ten days during the whole monitoring period), whereas some are observed almost daily.
Census, banding, and casual observation in a defined area over a one hour period are the principle methods used to monitor migration. Approximately 30% of the bird species noted at the observatory pass through or over winter in Central America, much like the humanoids on the Saugeen/Bruce Peninsula.
According to Mr. Steinacher, most migrating passerines are nocturnal. Accordingly, most are seen early in the morning as they land to feed and replenish their energy reserves. (He said that) This priority makes them appear ‘tame’ but this merely shows that they are driven to feed ‘at any cost’. The earliest spring migrants are water birds. Short-term weather patterns, particularly wind strength and direction, strongly influence migrating birds. A strong following wind may, for example, encourage birds to keep flying and pass over Cabot Head altogether.
During the day, when warming air rises, raptors can be seen using the mid-day thermal currents along the Niagara Escarpment cliffs. However, rain, fog and sudden changes in weather disrupt daily migration patterns causing birds to suspend their migratory patterns and land sometimes in less favourable habitats.
Mr. Steinacher reported that data from Cabot Head showed that in spring, passerine males arrive first to establish breeding territories. Females arrive later probably to pick mates in already established territories. He noted that in the fall migration, which includes the young of the year, the different timing of the sexes would be less significant.
Studying bird migration is labour intensive and the observatory always welcomes volunteers. Their website is at: www.bpbo.ca