Weekly Reports

This past week really typified what I always say about our station: the LSLBO is all or nothing. Many other stations are predictable in their levels of bird activity and have consistent day-to-day banding totals; not us, there is absolutely no predicting whether or not we will be busy. Some days we may count thousands upon thousands of birds but catch less than ten. Other days we will both see and catch tons of birds, or see nothing but catch lots. Still other days we don’t see or catch anything… Those days I dislike. For all but one day this week there was very heavy migration beginning right at sunrise and continuing steady throughout the entire day. Black-capped chickadees continued their strange irruptive migration- on a couple days we observed more than 600 individuals. Boreal chickadees also joined the fray. Typically we see only a handful of boreals in an entire year, one day this week we saw 70. Myrtle warblers also consistently exceeded 1000 individuals a day. Despite migration being very consistent our banding totals have been all over the map. The slowest day we caught 6 birds and the busiest we banded 80. This inconsistency has to do with the nature of why our station was established where it is. There are two different reasons why an area would have a particularly high number of birds making it a suitable area to establish a bird observatory. The first reason is that the area is extremely attractive to birds as a stop-over or breeding site because of high food availability. This is the case for many stations that are set up alongside marshes, wetlands or other areas of prime habitat, such as Beaverhill Bird Observatory or Delta Marsh Bird Observatory. The other reason is geographic funnelling – the habitat itself is not drawing the birds in, it is the adjacent habitat that is repelling them. The LSLBO has high bird numbers and diversity almost entirely for this reason; the birds don’t want to fly across the lake and they also don’t want to fly over Marten Mountain so they are funnelled along the shoreline of the lake. It isn’t that our patch of forest is bad habitat; it just isn’t anything spectacular and is no different than the rest of the forest along the 100 km length of Lesser Slave Lake. Because our site isn’t actively attracting birds it is all a matter of luck if they decide to stop and feed in our area instead of the countless other areas they could pick as they migrate along. If they don’t choose to stop and feed they just pass overhead well out of the range of our nets. Thankfully, although more birds pass over us than stop to visit the nets, we do still generally catch enough to keep us occupied; certainly enough to make taking time off a challenge. On one of my days off this week I was called in to help when a flock of 50 myrtle warblers all got caught in net six. I don’t mind losing the day off though since I know that very soon all the birds will be gone. One sign of the approaching end arrived this week – the first of the last – an American tree sparrow. This arctic breeder is always the very first bird to pass through in the spring and it is the very last species to pass through again in the fall.