The Waves of Migration

By Ryan Davis
For the past few months at the Missouri River Bird Observatory we have been very busy with fall migration banding. To date we have banded over 900 individuals and have been very fortunate to see a high amount of diversity and many cool birds. The main objective of operating a fall banding station is to gather data on migration ecology, including how long it takes each species to migrate south, their general body condition during the trip, and how long they stop to refuel before taking off again. These topics have been studied for decades using the same methods and there is a predictable pattern to how different guilds (groups of species based on common descent and/or life history traits) of birds will migrate.
The first group to start traveling south was the warblers. These small, colorful insectivores breed in north-central Missouri and further north, so the individuals that started showing up in our nets from late August through September could have bred locally or come from the Canadian tundra. We captured many of these quick-stopping and magnificent species, including (but not limited to): Canada Warblers, American Redstarts, Wilson’s Warblers, Chestnut-sided Warblers, Kentucky Warblers, Northern Waterthrushes, Magnolia Warblers, Black-and-white Warblers, and a lone Mourning Warbler. Some other warbler species, namely the Ovenbird, were captured for nearly a month in September while others didn’t arrive in our nets until late September and stayed for a few weeks, including the Nashville Warbler, Tennessee Warbler, Common Yellowthroat, and Orange-crowned Warbler. Most warblers have already moved through Northern Missouri and won’t be seen again until the spring, with the exception of the Yellow-rumped Warbler, which can still be seen in the area.
An adult male Common Yellowthroat, captured at Van Meter Marsh. 
Other groups which passed through earlier on in the season include the flycatchers and vireos, many of which could have also come from anywhere between Saline County, Missouri and northern Canada. We still occasionally hear some flycatcher species, the Eastern Phoebe and Eastern Wood-Pewee, at our Van Meter State Park sites, but these will soon move on to winter in the southeastern US.  Throughout September and early October we also captured high numbers of Indigo Buntings and Gray Catbirds, both of which haven’t been captured for the past few weeks.
 A Blue-headed Vireo, captured at Indian Foothills City Park.
As we started to catch less warblers, vireos, and flycatchers, the void was quickly filled, at first with thrushes and waxwings, and later with sparrows and kinglets. In mid-September we began to see Cedar Waxwings at our Indian Foothills City Park site and on September 23 we caught a flock of 19 individuals in only two nets. Since then we have captured one other flock and scattered individuals, but haven’t had any in a few weeks although we still see and hear them at Indian Foothills. Interestingly, we haven’t recaptured a single Cedar Waxwing despite our high number of captures and observation of them at our sites. This suggests that the flocks we see are composed of birds that are moving south for the winter, a steady stream of Cedar Waxwings from Canada and the northern US.

An adult Cedar Waxwing, captured at Indian Foothills City Park
Our first sparrow was captured within the first few days of October, and these ground-feeding seed-eaters have comprised the majority of the migrants that we have captured since. We have captured scores of White-throated Sparrows and only a handful of some other species, including the Fox Sparrow, Chipping Sparrow, Lincoln’s Sparrow, White-crowned Sparrow, and Swamp Sparrow. These torturously similar-looking birds are a little easier to identify in the hand, but still occasionally baffle us. Not too long after we began to catch high quantities of sparrows, Ruby-crowned Kinglets began to show up in our nets. These 4.25-inch, 6-gram acrobats feed on insects and winter in the southeastern US, amazingly surviving through snow and ice by spending cold nights clustered together to share body heat. The related Golden-crowned Kinglet is a winter resident of Missouri and has yet to show up in our nets, although we heard the first one of the winter at Van Meter Marsh just yesterday.
An adult White-crowned Sparrow, captured at Doc Morton’s Prairie near Cole Camp, MO for a Prairie Days festival banding demonstration.

Just as the leaves of different tree species begin to change at different times, we have seen wave after wave of songbird guilds come and go at our sites. Some species will stay here for the winter and others continue on a perilous journey southward, to Louisiana or Mexico or even the tropical forests of South and Latin America. We have been very fortunate to see each species come and go, and of course look forward to greeting them back in the spring.  

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