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Thread subject: Eagle Nest in Heron Rookery
Name Date Message
cathy 03/09/05 05:54 pm An interesting development from the Seattle area. There is a huge heron rookery (about 30 or 40 nests) tree in Renton, near Seattle. A heron advocate started "Herons Forever" to maintain the area for herons. She sent a message to a local bird email group recently stating that an eagle couple were building a nest in the heron tree and she wasn't sure what to think of this "new dynamic" (eagles prey on heron chicks). Today there was a strange development. She reported that 2 days ago both eagles were alive and well. Today, it is apparent that the female eagle is dead in the nest. Here is her note:
Yesterday we discovered that the female bald eagle nesting next to the herons was dead. We had seen her and her mate the day before and both appeared to be in good health. We very much need your help monitoring this situation.

Her mate is close by, standing watch over her. His behavior is
fascinating. This pair may have been together for several years according to one source who has been watching them. We want to know what happens next. Will the mate remain there with his mate? Will he try to push her body off the nest in order to try to re-nest with another female? We just don't know what will happen next. But we do need people to watch this

We are arranging to remove the female but need to wait. Right now the herons are acutely sensitive to any disturbance, so we want to wait until they are incubating eggs, when they are a bit less sensitive.

Please help if you can, even if it's for a short time. You may see
something absolutely astounding during that time. It's likely, in fact. Reply to this email and I'll receive your response.

Thank you,
Suzanne Krom, President
Herons Forever

Cathy again: I used to work near this rookery and noticed from my office window that eagles and red-tailed hawks were hanging out there in the Spring. I always thought how it is difficult to know what to think when 2 predator and habitat-threatened species start competing. Animals need our advocacy, but are we the ones to decide which animals get the scarce resources, or are they?
Fred W! 03/09/05 06:35 pm We'd be interested to eventually find out the cause of death, whether 'natural' or nefariously otherwise!
karen 03/10/05 08:33 am cathy thanks for the post ... it is an interesting question you raise and no clear answers nature can be cruel but man has so messed some up parts of the cycle that we do bear some responsibilty ... please post any updates if they find out what killed the female eagle ... thanks
Marie 03/10/05 09:31 am Cathy, that is an interesting and sad story for the eagle pair. Hopefully it was just a case of 'old age' for the female and not anything more sinister. Do keep us posted.
Suzanne Krom 09/21/05 04:39 am I noticed your posting about our heron colony and thought I would give you a followup report about the bald eagles. But first, Iâd like to correct the number of nests in the Black River colony. For the past several years, we have constantly had about 130 active nests each season, not the 30 â 40 nests reported above.

The dead femaleâs mate remained close by her side for about two weeks, frequently calling to her and occasionally going into the nest and appearing to attempt to awaken her or get some response from her by pulling at her with his beak. He left infrequently for short periods, up to ~10 minutes at a time. Occasionally he appeared to be attempting to push her out of the nest but because of her weight, he was not able to cause her to move .

Two other eagles joined the male, one was an immature (first year) and the other a subadult (second year). They visited frequently and perched in the same trees together, on separate branches but within ~100 feet of one another.

At the two week mark, the surviving mate left for about two hours, returning with a mature female. We were amazed at how quickly he was able to find a replacement mate. It was as if there was a bulletin board somewhere for mature eagles looking for new mates. But it was nesting season for him and itâs likely that he didnât want to lose an entire season. Within 5 minutes of arriving at the nest, the new female jumped into the nest and took a tentative bite out of the dead bird. She shook her head as if the taste was unpleasant but then took a second bite, then a third. She called to her new mate and he joined her. Together they cannibalized his former mate, who had been dead by then for about two weeks. During this time, the temperatures were unusually warm, into the mid 70s, so the decay must have been fairly well advanced.

After most of body had been consumed, they left and were not seen again during the 2005 nesting season. The herons then raided the eagle nest for sticks.

We decided to not investigate the cause of death as it would have been extremely disruptive to the herons. The most likely causes would be related to egg laying â egg binding or a condition where a bit of the yolk escapes into the body of the female. Either condition is deadly. We decided that in the end, it was not that important to know what the cause of death was. The greatest benefit? âThis was a rare opportunity to watch this remarkable dynamic unfold.

Regarding how we would have responded to this prey-predator nesting situation in close proximately, we were going to take a hands-off approach and record our observations with as much detail as possible. Much of their habitat has been eliminated, meaning they are all competing for far scarcer resources, including nesting trees, quick access to plentiful food, and safety from human disturbance and other threats.

I believe that another question should be asked as well: Why did the eagles choose to nest in this colony, when they showed no previous interest in doing so before during the colonyâs 16 years of existence? An office development was recently built within 500 feet of the colony. The section of the colony closest to the development had always been the primary location for the colony. After the development went in, eagles started predating the herons in this section. Over the course of the past three years, the herons moved ~200 feet away, into a swath of cottonwoods that were now the only other trees available to them for nesting. 2004 was the first year that no herons nested in the compromised location. This was exactly where the eagles chose to nest in 2005. Eagles are opportunistic feeders and take advantage of compromised ecosystems. The developers like to blame the eagles for causing the herons to abandon this section of the colony but its important to look more closely at the cause and effect.
Suzanne Krom, president
Herons Forever
Renton, WA

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Tom Throwe
Last modified: Sat Feb 18, 2006