MLNP banding update, early October

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The last few days of banding at Muskegon Lake Nature Preserve have been fairly slow. This has been partly due to the clear skies, under which netting success is drastically reduced. However, this can also be blamed on the relative paucity of incoming migrants. As you can see from the Nexrad radar imagery, the bulk of the passerine migration on Wednesday night was further west.

The disparity was due to the high pressure ridge located over Minnesota. During autumn, the best flights generally occur on the east side of a high pressure system. An accompanying cold front provides an impetus, the clockwise rotation provide favorable tail winds, the cool and reasonably tranquil weather facilitate powered flight, and the clear skies aid navigation.

On a local level, flight conditions have been almost as conducive to long flights, but with relatively few birds emanating from Canada, the preserve has hosted fewer birds with each subsequent day. The following image shows the SSE orientation and the fairly rapid velocity of Wednesday night's migrants.

Birds that are remaining at the preserve are gaining fat and mass at a very rapid rate. With lower densities and abundant forage, rest and fuel is readily available, and stopover migrants can balance prolonged stays with potentially much longer flights. Nevertheless, new birds do appear every day, and today offered a small surprise.

While the species is currently appearing in good numbers at the Muskegon Wastewater and other grassland habitats, this Savannah Sparrow provides a first record for Muskegon Lake Nature Preserve. Given the brushy habitat at the site, other sparrows are more typical.

Swamp Sparrows generally remain in the cattails, but a few do wander into the net lanes.

Lincoln's Sparrows are fairly common at the preserve. I have banded seven so far this fall, but none since September 27.

White-crowned Sparrows are one of the most common species at the preserve, and I capture an unusually high proportion of adult birds. In fact, it is the only regular breeding species or migrant in which adults outnumber hatching-year birds. Most individuals belong to the eastern race, characterized by black lores. However, I do catch a few Gambel's White-crowned Sparrows, a white-lored subspecies which breeds further west. This year, possibly due to those amenable weather conditions keeping such birds west of Lake Michigan, I have only captured one.

- Brian Johnson
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