09-02-15 Bird Field Note

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09-02-15 Bird Field Note

September 2, 2015

Eric Rasmussen compiled this weeks bird field note. The note shows hummingbird banding, songbird banding with UMBREL, and a research update on Lewis's Woodpeckers from William Blake.

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Bird Field Note 8/28/15 Compiled by: Eric Rasmussen

I recently completed a week-long hummingbird banding workshop in New Mexico, and will be able to operate a banding station at MPG next year. In this photo, I examine a male Rufous Hummingbird.

Hummingbird banding requires specialized equipment adapted from jeweler’s tools (top photo). Accurate measurements take a steady hand and precise placement of the tools (below).

Distinguishing the age and sex of particular species may depend on the width of a tail feather (above). Checking for fat on the belly provides insight into the health, food availability, and migration behavior of hummingbirds (below).

Banding the bird while it is in the net prevents escape and injury. In this photo, I use a gauge to measure the bird’s leg and choose the correct band size.

Gentle, but secure handling keeps hummingbirds still and comfortable.

Hummingbirds remain fairly calm during the 3-5 minute banding process. Before release, they receive a nectar reward.

During the first week of fall migration banding, we captured 481 birds of 46 different species. More than half of the captures occurred at the Floodplain station (low elevation, 254 captures), followed by Sheep Camp (mid elevation, 123 captures) and the Ridge (high elevation, 104 captures). Regional wildfires made the air quality poor; smoke levels shifted from moderate on Monday to very thick by Friday.

Bird feathers are durable, but sun, weather, and use cause wear and fading. To compensate for wear, adult songbirds molt in the autumn, replacing every feather on their bodies. This Yellow-rumped Warbler is in the process of molting; the year-old feathers are worn and light brown (outer edge), but the new feathers are fresh and dark.

Townsend’s Warblers have been unusual captures in the past, but this year we caught 14 of them during the first week of banding. This total exceeds captures from the entire 2014 field season.

Wilson’s Warblers are among the smallest warblers in North America. Males grow an extensive black cap during their first year. Females, like this one captured at the Ridge station, sometimes develop a limited cap.

We caught this young Spotted Towhee at Sheep Camp on 8/17. It had a deformed mandible and lacked a right eye (the left eye was normal). We processed the bird, noted the malformations, and released it. Three days later, we recaptured it and it had gained weight, suggesting it is able to forage successfully.

Research Update: Lewis’s Woodpeckers William Blake

We have completed our third year of Lewis’s Woodpecker nest monitoring. This year, Lewis’s Woodpeckers initiated nesting earlier than in previous years. Because 5 nests failed and some pairs attempted second nests, incubation and nesting periods spanned a longer time in 2015 compared to previous years.

We saw lower nesting success on MPG Ranch floodplains this season compared to 2014; five of 13 nests failed. We found evidence of predation at two nests (below). A Hooded Merganser took over one nest, and two others failed for unknown reasons (potentially hunger or heat stress). The higher count of nest failures this year may also reflect better detection due to increased monitoring. Despite these failures, we saw higher nesting success at MPG Ranch compared to that reported in similar habitat in Colorado, where 46% of nests fledged young*.

We want to know if nest success varies by habitat type. We saw variable, but high, nest success across our study sites, with no clear difference between floodplain and burned forest sites. Across all sites, we observed the lowest nest success at MPG Ranch. Though we think predation and heat stress caused most nest failures, we do not know why these conditions would be different at MPG Ranch.

We filmed every nest once during incubation and three times during the nestling period. This effort produced 134 videos and 800 hours of recorded observations. This fall we will analyze the footage to study parental investment behaviors like prey delivery (below). No one has examined how Lewis’s Woodpecker feeding rates or food size might explain variation in nesting success.