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Archived Postings

July 10, 2008 – July 16, 2008

Every year it seems to start far too soon, but I am thrilled about it. I am referring to fall migration. That’s right, fall migration is upon us. The LSLBO opened the migration station on July 12 to monitor bird populations as they head south for the winter. Monitoring will occur every day until the end of September, a span of twelve weeks. The duration of fall migration is much longer than spring migration, which lasts six weeks, for several reasons. First, there is a high variability in the length of time that species need to finish their breeding activities. During the first week of migration we were catching fully independent juvenile birds while still finding active nests. Another reason is that both adult and young birds complete a moult before they commence with migration, which also takes a variable amount of time depending on species and age class. Adult birds go through their pre-basic moult, which means they replace every feather they have. This is done in stages and can take a couple weeks to complete. Young birds go through their pre-formative moult once they leave the nest. They replace their juvenile plumage and a few of the wing feather tracts that are susceptible to increased wear. Fall migration banding is busier than the spring because of all new birds born in the summer. There are simply more birds in the area. It is estimated that four times as many birds migrate in the fall than in the spring. This means that with more birds around, often moving together, banding can become very busy, very fast. There have been times when thirty young Tennessee warblers have hit a single net at one time. Fall migration also offers some identification challenges. Young birds are still in juvenile plumage during the early stages of the fall. Juvenile plumages often lack solid identification features and can be almost identical in species within the same family. This makes identifying sparrows a lot more interesting. Finally, we still have two rounds of the MAPS program to complete. On days when migration and MAPS overlap we are operating 22 nets and flocks of young birds can hit any of the nets at any time. It is a very challenging time of year at the banding station. We begin fall monitoring mid-July to capture the full migratory window, we want to start before any major migratory passage occurs. Even then, within the first few days we observed birds actively migrating. Chipping sparrows, Tennessee warblers, yellow-rumped warblers were some of the species migrating. Banding through the opening week was steady, but not hectic. We banded 133 birds from 25 different species. The top species captured were yellow warblers, American redstarts, black-and-white warblers, ovenbirds, and Tennessee warblers. Some of the heaviest songbird migration of the year occurs late in July. Over the next few weeks we can expect some great days of bird banding.

2010