Prairie Bird Nest Monitoring at Taberville Conservation Area
By Katie Leonard, Nest Project Crew Leader
The nesting period of most grassland-obligate birds ranges from mid-May through mid-July, and they often have at least two broods during the season. We have been nest-searching at Taberville Prairie Conservation Area since the end of May. Our target species include Dickcissels, Field Sparrows, Eastern Meadowlarks, Grasshopper Sparrows, Henslow’s Sparrows, and Bell’s Vireo. We have found the highest number of Dickcissel nests, reaching thirty-nine, and the season is not even complete yet! We have found eight Field Sparrow Nests, four Eastern Meadowlark nests, and eleven Bell’s Vireo nests. Other species nests we have found include Brown Thrashers, Mourning Doves, Red-winged Blackbirds, Common Yellowthroats, Orchard Oriole, and an Eastern Kingbird. There is a lack of Grasshopper Sparrows, so we have not found any of these nests. The other aspect is Grasshopper Sparrows are very secretive when it comes to keeping their nests hidden, as are Henslow’s Sparrows. Though we have only found one Henslow’s nest, we know there have been more due to observations of multiple pairs feeding and other nesting behaviors.
We have been searching two different areas at Taberville. Both have been ‘patch-burned’, but one area is grazed upon by cattle while the other is not. We spend equal amounts of time searching for nests in both areas, and so far there has been a higher number of nests found in the grazed area. Although we have found seventy nests so far this season, the rate of nest success is very low due to depredation occurring. Snakes are the main predators of nests at Taberville, but there have been a few cases of mammals depredating nests. There have also been a number of nests that have successfully fledged chicks, which is indicated by an empty nest with fecal matter in it and very vocal adults in the area.
Brown-headed Cowbirds create a different type of obstacle for these birds. They are brood parasites, meaning they lay their eggs in other birds’ nests. Brown-headed Cowbird chicks are often more successful than host chicks: they are usually larger and often hatch earlier than host species. Therefore, they are better at obtaining resources from the adults. So far we have observed parasitism in Field Sparrow, Dickcissel, and Bell’s Vireo nests. The parasitized Field Sparrows and Dickcissels still will incubate and raise the cowbird chicks. In contrast, each Bell’s Vireo nest that was parasitized has been abandoned.
We still have time to find more nests, so we are excited to see how the rest of the season goes!