09-23-14 Bird and Bat Field Note

09-23-14 Bird and Bat Field Note

September 23, 2014

Debbie Leick's Field Note shares updates on nocturnal flight call monitoring, raptor counts, songbird and raptor banding, plus bat house installations.

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Bat and Bird Field Note Bat Houses, Nocturnal Flight Calls, Raptor Counts, Songbird and Raptor Banding 9/21/14 Debbie Leick

Bat Conservation International (BCI) provides detailed guidance on bat house construction and placement. Their research shows that boxes placed within ¼ mile of an open water source and near diverse habitats have higher occupancy rates. This week we installed bat houses at the locations shown below based on these recommendations.

Gus and William installed one of the boxes on the Orchard House barn (below). Boxes placed on buildings or poles attract bats more often than those hung on trees. BCI’s studies also show that bats like it hot; William painted the houses black to maximize heat absorption.

Gus used the bucket truck to place this bat house as high as possible. Guidelines recommend placement at least 12 feet off the ground and at least 20 feet away from obstructions such as branches and power lines. Bats occupy the majority of installations within the first year.

In August 2013, our acoustic monitoring stations recorded 656 nocturnal flight calls from migrating sparrows and warblers (“tseeps”). This year, detections nearly tripled with 1809 detections.

When we compared the daily call totals to barometric pressure, August 2014 showed stronger dips and rises indicative of more unsettled weather (Figures 2 and 3).

Increases in nocturnal flight calls coincided with precipitation events (Figures 4 and 5). We plan to incorporate weather variables into all future nocturnal flight call analyses to see if these patterns persist.

A red crown patch on a Ruby-crowned Kinglet indicates a male (arrow). During the breeding season, this energetic species spends most of its time in the treetops. In the fall, they stay closer to the ground, which allows us to capture numerous individuals.

This White-crowned Sparrow displays the black-and-white “racing stripes” characteristic of an older bird; young birds display the same pattern, but in a tan-and-brown coloration. Five subspecies of White-crowned Sparrows exist. Gray lores and an orangish bill identify this bird as a Gambel’s White-crowned Sparrow.

Common Yellowthroats provide a classic example of sexual dimorphism. Females (above) display drab, indistinct yellow and olive-brown plumage. Males (below) exhibit brighter plumage with a distinct black and gray facial mask.

People often mistake Pine Siskins for sparrows due to their brown, streaked plumage and thick bill, but they belong in the Finch family. Pine Siskins exhibit irruptive migration; instead of predictable annual movements, they migrate wherever food resources are available.

For the first time, a warbler species surpassed the sparrows in sheer numbers; Yellow-rumped Warblers occupied the draws in numbers well above our previous observations. Vesper and Chipping Sparrow numbers decreased.

Large flocks of American Pipits foraged on insects in the former crested wheatgrass areas.

This week we had three 100+ count days (Sept. 9, 12, and 15). Top birds included Turkey Vultures, American Kestrels, and Cooper’s Hawks. We expect Accipiter numbers to continue increasing over the next two weeks. Buteo and Eagle numbers should increase in October.

We captured 15 raptors, with similar numbers at both sites. We caught more Falcons at the lower Indian Ridge station, and more Accipiters at West Baldy Ridge. Based on the visibility of our lure birds and the observed behavior of migrants, we think we may capture more birds at Indian Ridge than at any other previous MPG trapping site.