Grasshopper Sparrow totals, July 31

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July ended on a high note for Grasshopper Sparrow banding at the Muskegon Wastewater. Yesterday, I caught 9 (8 new, 1 recapture) sparrows in 90 minutes, which resulted in a total of 65 individuals captured so far this year. Of these, 15 were returns from 2008 or 2009. Despite the good capture rate, densities were far below what they were the last two years. Due to the compromised habitat, there are fewer territorial males and less suitable nesting structure across the study site. However, juveniles were well represented among July captures, so productivity may have been good at the Wastewater overall.  One of the captured Grasshopper Sparrows had initiated its pre-basic (post-breeding) molt. This was the first molting sparrow I have observed this year.

In the case of Dickcissels, throughout July there have been at least seven territorial males south of Apple. Two of these birds found their way into my nets. In the last few days, their song activity has rapidly diminished. Young Bobolinks have become numerous along Swanson Road. The influx of juvenile birds, song cessation, and the start of feather replacement indicates that the post-breeding season has arrived for the majority of grassland birds. However, as in the case with certain single-brooded species like Brewer's Blackbirds, most of which vacate the area in early July, some have started this phase of the annual cycle earlier. This post-breeding / pre-migratory period is a poorly understood part of a bird's life cycle. The numbers of terrestrial insects are dramatically increasing, and it is this forage base that will fuel molting and migratory fat deposition among birds. (Upland Sandpipers and most swallows, unlike other local grassland species, accomplish most of their molt on their winter grounds, so they rapidly depart in late July and early August.) But because birds are becoming quiet and fairly reclusive - patterns exacerbated by dense vegetation and hot, humid birding conditions - their general behavior and movements are not easily observed for the remaining weeks they are here.

- Brian Johnson
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