MLNP mid-October Banding Update

.
As testament to the advanced stage of the migratory season, numbers of Long-tailed Ducks are building offshore, more overwintering landbirds are arriving daily, and neotropical migrant passerines are very nearly gone from the Muskegon area. Although most individuals have recently left, sparrow diversity has been quite high at the Muskegon Lake Nature Preserve, and on October 12 two new species (first and third photos) were captured.

Although Fox Sparrows rarely overwinter in Muskegon County, this northern species arrives later in the fall and earlier in the spring than most other sparrows.

Compared to the other small thrushes, Hermit Thrushes are shorter-distance migrants that are much more tolerant of cold weather. They have been rather numerous these last few days.

This American Tree Sparrow is one of the earliest fall records from Muskegon County. A second was caught on the 14th. This is the only nominate sparrow that regularly winters in Muskegon County (Dark-eyed Juncos and Snow Buntings can also be considered sparrows).

Field Sparrow passage coincides with slightly warmer weather than that for Fox Sparrow. The species is a fairly common breeder and a rare winter resident.

I have noticed that migration seems unusually advanced this autumn. This has been evident for both long and short distance migrants. For instance, White-crowned Sparrows have peaked 9 days earlier than average at the Preserve. Curious as to any long-term trend (or lack thereof), I compared the passage dates of White-crowned Sparrows from my banding operation (2006-2010) to those banded by Larry Walkinshaw in Laketon Township (1960-1979). His average date of passage was October 6, three days earlier than the recent mean.

Contrary to popular belief, the accelerated phenology this fall has more to do with warm weather than cold weather. While it may seem logical that prolonged cold spells or an upcoming hard winter would force birds to vacate earlier, this really is not the case. A mild winter and spring at the beginning of 2010 induced many species of temperate migrants to return to the breeding grounds earlier than typical. As the spring progressed, warm temperatures promoted bountiful insect populations which favored a quick transition from the migratory to nesting phases among both temperate and neotropical migrants. Continued food abundance generated by the summer heat likely promoted a faster breeding cycle, a speedy molt, and rapid pre-migratory fat deposition. The warm, placid weather this fall has kept food resources high and energy expenditures lower.

- Brian Johnson
.