Thursday, June 20, 2013

June 20

16 day old nestlings

Very fierce falcon wannabe 24 day old nestling

     a full box of 5 nestlings 20-24 days old with prey remains (song sparrow) left in the box by the adults

a close-up of the song sparrow left in the box by the adults

Annie and I with the first nestling this year to be outfitted with a radio transmitter for telemetry purposes

     After a little bit of a lull waiting for the young in the earlier boxes to develop enough to be banded, things are starting to pick up. Twenty-three nestlings have been banded to date. The broods have contained either 4 or 5 nestlings, which is the norm. You can see from the photos that the development of the young progresses very rapidly. The changes in appearance in the nestlings as they develop is remarkable. That is evident when you look at the photos of the nestlings above. The ideal age window for banding is 16-18 days old. If you remember from previous posts, this is calculated by dating forward from the appearance of the first eggs in the box. It is not always an exact science, but it can get you close. There are times when, for many reasons, one can be surprised upon opening the box. What you expect to be 16 day old nestlings looking at you can, in fact, be birds that are barely able to lift their head or birds that are nearly ready to jump out and join the big, bad world. Speaking of which...............I don't think I have mentioned this in other posts, but the expected mortality of first year birds is as high as 80%. Imagine thinking about the fact that, after all this work since March 8, probably only 1 out of every 5 nestlings will survive to breed next year. It is not something I tend to dwell on much. From the photos it is also obvious that the youngsters need a little help in the keeping their bedroom clean department. Actually, the center area of the box where they spend most of their time huddled is actually quite clean. Like many nesting raptors, these young are programmed from birth to back up to the outside edges of the nestbox and squirt their feces in an outward direction away from the center of the nest. This results in having the inside walls of active nestboxes completely covered with whitewash. One of my favorite jobs every March is opening the boxes to scrape off all the whitewash of the walls of the boxes. Ina howling, freezing wind it doesn't get any better than that. 
The prey delivered to the young consists mostly of insects, with the occasional meadow vole or small songbird tossed in for good measure. In my experience, it is the males who tend to deliver the largest prey items to the box. They don't show up often.......maybe once for every 40-50 visits by the female, but they deliver the goods when they do. The last picture today shows Annie and myself with a 28 day old male who has been outfitted with a radio transmitter for telemetry purposes. I don't have the time to discuss this topic now, but will cover the telemetry aspect of our work this year in a future post. I'm hoping to get to that post written fairly soon so I don't get chastised in Latin again for not posting more frequently :)