04-29-15 Bird Field Note

04-29-15 Bird Field Note

April 29, 2015

Debbie Leick's field note details spring breeding, nocturnal flight call monitoring, and raptor migration.

Bird Field Note Spring Breeding, Nocturnal Flight Call Monitoring and Raptor Migration

Kate and William observed the pygmy-owl pair mate three times on Monday, April 20th. Based on the presence of three eggs in the cavity on Wednesday, we suspect they initiated the nest sometime on Monday afternoon.

Kate photographed the banded male Bald Eagle from the clubhouse nest. Cherin from RVRI has been checking the nest daily and thinks the eggs may have hatched about 2 weeks ago. She noticed two hatchlings this week.

Lewis’s Woodpeckers appeared at the suet feeders on Friday, April 24th. We will watch for colored leg bands.

A European Starling investigated the swift box in Sheep Camp.

Gus designed a new mast that allows us to compare Old Bird’s 21c microphone to Wildlife Acoustic’s nocturnal flight call (NFC) microphone. Nature Sound Electronics modified the Old Bird mic to work with the Songmeter recorder. The 21c uses a method to amplify sounds that can result in two to five times as many recorded nocturnal flight calls.

I processed the first night’s recordings with Old Bird’s “tseep” and “thrush” detectors and found better performance from the 21c microphone. A Sora call from the 21c (above) showed stronger amplitude than the almost invisible call from the NFC mic (below).

We recorded our highest counts for 2015 this week, including 77 passing migrants on April 21. Red-tailed Hawks made up a large portion of this week’s total, though they were outnumbered by both Cooper’s Hawks and Sharp-shinned Hawks. We also recorded our first Broad-winged Hawk and Swainson’s Hawk this week. We expect our weekly totals to remain high through the first days of May.

This Prairie Falcon passed right over our observation station. The dark feathers in its wingpits help distinguish it from a Peregrine Falcon.

The Osprey Rapunzel, banded at the Ranch Entrance Nest in 2012, is now a full adult and began her northern migration on April 20th. Though most Osprey in the region have already arrived at their nests, we hope to see her rear her first brood of chicks this summer. Last year she left her wintering grounds on May 11—far too late to hold down a nest and raise a clutch of young.