[Tweeters] Re: A Question re Bald Eagles and Nesting

Martin Muller MartinMuller at msn.com
Sun Nov 21 15:26:56 PST 2004

Mary Klein asked about Bald Eagle nesting activity (nest building specifically) this time of year.

Based on many years of detailed observations in the greater Seattle area here's a rough calendar for Bald Eagle activities:

February: much nest building, copulation, territorial defense; both adults bring in sticks (up to 10' long, no typo), line nest cup with grasses.

Early March: egg-laying at 3-day interval (most commonly 2), start incubation by both adults after 1st egg.

Mid-April: after 35 days of incubation, hatching of eggs at 3-day intervals. Both adults brood chicks and feed them chunks of prey (no regurgitation). Chicks start thermoregulate at 2 weeks, adult attendance starts to decrease.

Late May: chicks at 6 weeks start to tear up own prey. Adults no longer feed chicks.

Early-July: At 11 weeks (12 for single chicks) chicks start to fly (much variation possible due to collapsing nests, sibling rivalry, etc.).

Mid-to-late-August: Chicks leave nesting territory on their own. Adults start heavy molt and become very wary and notoriously hard to find. Fledglings head for rivers with salmon runs. One year a 10-week-old nestling had fallen out of its nest. It was put back in nearby tree (after veterinary check-up at Woodland Park Zoo). Adults fed it and it fledged "normally". It had a transmitter attached to tail in case it got in trouble again. It flew north. Its signal was last heard at Deception Pass (north end Whidbey Island) 24 hours after leaving Seattle.

November-January: Adults on territory do courtship and nest maintenance/building. Most (if not all) of our local (adult) eagles stay on territory. Nest trees are in short demand; the climate is mild; there's plenty of food. Why migrate?

In other words, Mary, it is perfectly normal to see eagles working on their nest at this time of year.

Martin Muller, Seattle
martinmuller at msn.com

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