Adventures With Vireos

Every couple of weeks I am fortunate enough to take a few folks out where I work to go bird watching. Plumbeous Vireos are always a good catch, though they are frequently heard but difficult to find high up in the pines.

Adult Plumbeous Vireo (Vireo plumbeus)

The last time, two weeks ago today, we heard one calling and saw it fly into a relatively short tree - where we found a nest:

Plumbeous Vireo nest

Expecting the typical stick and twig construction, what we found looked similar in many ways to a hummingbird nest, only MUCH larger. Bits of plant matter held together with spider webs, it was only about 7 feet above the forest floor.

I couldn't get back for a couple of days, but found the parents feeding their newly hatched chicks regularly - note the yellow-orange bill, just barely visible, reaching up for a fresh, juicy bug.

The nestlings must have been pretty small and unable to self-regulate their body temperatures at this stage as an adult would sometimes sit on the nest.

It would be another five days before I could get back again, and the young ones were really growing fast, the adults were working feverishly catching insects and bringing them back to the nest.

Two days later (July 4), the feeding continued, here the parent bringing what appears to be a moth . . . 

 . . . followed a few minutes later by this huge caterpillar!

Later that afternoon I returned with my video camera in hopes of getting a little video to go along with the stills, only to find the nest was empty. I could hear the adults calling and, softly, the now fledgling Plumbeous Vireo chicks begging. Though never completely certain, I thought there were four in the nest, but could only find three as I followed the sounds they were making.

One thing that took me by surprise was that they were not together, unlike other fledglings I've seen. I plotted their locations with GPS coordinates and Google Earth as you can see above. I found them to be anywhere from 50 to 90 feet away from the nest and well separated from each other. It would be interesting to know if this is normal strategy and, if so, for what purpose. Is it to increase survival rates by reducing the chance of all being taken by a predator, or to reduce competition from siblings for the parent's attention for food? I hope to find out . . . 

I did get some video, too. This is PLVI #1 on the map above, who I found in some brush very close to the ground next to a busy hiking trail. It'll be in a tree toward the end of the clip, as I chose to get it up a little higher and away from people. Truth be told, the adult was scolding me rather harshly when I first picked the chick up, but calmed down and began singing, rather sweetly actually, after I placed it in the tree and backed away from the chick. Another thing about the video is to note how stubby the wings are - they couldn't fly much, but did hop from branch to branch while flapping their wings. Their gone now, though the last time I saw them they were still not flying all that well, but moving from tree to tree following the parents around.

All in all a great experience for me, and here's hoping they live long and productive lives . . .