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 Third Juvenile (Intruder) at White Rock Nest
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By: davidh (offline) on Saturday, July 21 2012 @ 03:50 PM EDT (Read 819 times)  
davidh

Hi All:

Some thoughts on the new bird at and being fed by dad at White Rock.

I have been told, though not yet seen the video, that a third chick of the year has not just appeared on the White Rock nest but that Dad actually, after some hesitation, actually fed the new arrival. Unusual I suspect and quite wonderful to have this recorded.

Obviously the first question is where did this chick come from? Of course without banded birds we don't know for sure but this new chick, individually identified by different wing markings according to Christian, has been seen to fly back to the nest immediately south of the White Rock territory. As I have pointed out many times Boundary Bay is probably the most productive bald eagle habitat in the world. I have over 80 nesting pairs between White Rock, through Surrey, Delta and south to Point Roberts, Washington. All along the Crescent Beach cliffs, with our White Rock nest in the middle, are 8 active pairs with a couple of nests closer than a half mile apart.

Between our cam followers and the two keen ground observers, Tina and Christian, we are getting an interesting picture of how so many nesting pairs, and sometimes up to another 1500 transient eagles, share this area.

Back to the two chicks and the third intruder. I suspect, as Christian has observed, that this extra chick is from the immediate nest to the south. It was Rosana who finally spotted this nest - probably its second year. Is it possible that our pair, who for years nested 1/4 mile north before relocating on the present tree that we prepared for them, knows these neighborhood parents sufficiently to allow their young to settle into their nest? Could the adults to the south be offspring of our pair? When our pair nested the 1/4 mile north they had a bad last 3 years -- having their nest tree chopped down 3 years in a row. Before that for many years they had annually produced 2 young per year. Then they moved into the current tree, in which we prepared the foundational branches. My question is did this move the pair closer to another pair? A pair they knew? Their offspring? With so much natural food available below them in the Bay, perhaps they are less competitive and more tolerant.

For dinner last night we had Christian and another biologist and the conversation turned to the White Rock nest with three juveniles, one of which was a stranger. Ildiko, who just got appointed as Associate Curator at the Cowan Vertebrate Museum, reminded us that several records exist of different raptors taking young raptors from other species nests, presumably as a food source, but then once carried back to their nest site, the "begging response" of the potential prey now stimulated its captor to feed it. Perhaps we have a similar situation here. While the neighboring juvenile, when first landing on the White Rock nest seemed to be greeted with some hostility, is it possible that its begging response overcame the aggressive response of the parent? It is quite possible that our live cams will yield some further insight into this interesting behaviour.

I will quickly add that when a young gosling or heron chick is brought back to the nest by the eagles that "their response" is not met with the same positive reaction!

Please gather up some of the images of the 3-some. Christian is going to give me wing shots individually identifying the 3 young.

Thanks.


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