Sunday, April 29, 2012

Bluebird Trail, Week 5 - Pink Eggs, Tree Swallows & More

We now have 15 nestlings and 13 more eggs among the 18 boxes we are monitoring at 11 sites. It's also clear that one of our bluebird nestboxes has become a tree swallow nest.

Papa bluebird has a caterpillar for the Box 9 babies

As I reported midweek, all five eggs did hatch at the first site, Box 9, and five more hatched a day or two later at Box 16. Now we also have five nestlings at Box 14 that hatched probably Thursday or Friday. It got pretty cold this week, but they all appear to be okay. I could hear tiny cheeping coming from the two boxes with the oldest nestlings, which was delightful. Once again, my camera's start-up chime got several nestlings to gape (below). That one at the top left doesn't look too vigorous, but it may just be the angle.

Box 16 - Nestlings Day 5 - note darkening where feathers will grow

Last week we started to suspect that Box 15 was being used by tree swallows, as we saw one making territorial swoops past the nestbox. This week it was confirmed, as I saw swallows landing on the house and, as you can see below, even emerging from it. I took the photo below from the car and then drove on to check another box rather than disturb them when they were so active at the box. When I came back they were not in sight, so I checked the box and found several prominent feathers in the nest, but no eggs yet. Bluebirds sometimes incorporate small feathers to line the grass nest, but tree swallows routinely use larger feathers and more of them.

Tree swallows at Box 15 (note one emerging)

During our mid-week check we found two eggs in one of our newest nests, Box 18, that at first led us to question whether this was indeed a bluebird nest. We had heard that a small percentage (perhaps no more than 7 percent) of bluebirds lay white eggs rather than blue. These eggs looked the right size and shape (tree swallow eggs are somewhat more pointed at one end), but they had a pinkish color, which was unexpected.

Though usually blue, bluebird eggs can be white, or even pinkish - Box 18

There was an agitated pair of adult bluebirds on a wire directly overhead, so we were fairly sure this was indeed a bluebird nest. We confirmed at the very helpful bluebird website that bluebird eggs can indeed be pink! I was there again today and found there are now three pink eggs, and mama bluebird (again on the wire) was most perturbed that I was looking into her nestbox, so I didn't linger to take another photo.

Here's the full report for the week.  Boxes retain the same numbering all season, so even though two boxes have been taken over by another monitor we keep them in this list so the numbers will stay correct. We were invited to take on two more boxes this week, and were also asked to temporarily monitor some in another location, the latter of which I have not added here. Calculations of incubation time are based on Sunday's early-afternoon nest check.
  1. We saw a pair of house sparrows at these two boxes earlier this week, and a partial nest was built. We set the sparrow trap but have not had luck -- but the sparrows seem to have been discouraged from this nest.
  2. (Paired with #1) No activity.
  3. Partial nest - no change. 
  4. (Paired with #3) Nest about complete, no eggs - little or no change. Tree swallow noted nearby.
  5. Five warm eggs, estimated to be 11 days into incubation, with hatching anticipated in the next 1-3 days. Male noted flying from the area of the nest.
  6. (Paired with #5) Partial nest - no change.
  7. Partial nest - no change.
  8. (Paired with #7) A few strands of grass - no change.
  9. Five nestlings approx. 7 days old  - starting to look much darker and less naked. Tiny cheeping sounds from closed box. Four had hatched on our visit a week ago, and the fifth had hatched by the time we visited again midweek -- probably only a short time after the others.
  10. (Paired with #9) Complete nest, no eggs  - no change.
  11. Discontinued  
  12. Discontinued
  13. Five warm eggs - a week ago there were three cool eggs. Incubation probably five days along, with hatching anticipated in 7-9 days. Bluebird flew from box.
  14. Five nestlings approx. 2-3 days old (they had not hatched as of Wednesday when we stopped by).
  15. Full nest, no eggs. We now think this is a tree swallow nest. Tree swallows were observed on top of and inside the nest box (see photo above), and the nest contains several prominent feathers, which is characteristic of tree swallow nests.
  16. Five nestlings approx. 4-5 days old, cheeping; both adults vigilant and agitated nearby. 
  17. Chickadee nest contains substantial bed of moss, but no change for the past two weeks.
  18. (Paired with #17) Three pale pink eggs, warm (?). There were two eggs on Wednesday, so since bluebirds lay one egg per day it may be presumed the clutch is complete. If incubation began Thursday, they are 3 days into 12-14-day incubation, with hatching anticipated in 9-11 days. One egg at least felt warm; I wasn't sure if they all did. Adult female watchful and agitated nearby.
  19. New box this week: A few strands of grass.
  20. New box this week (paired with #19) A few strands of grass.
Follow the full saga of our bluebird trail at my Bluebird Trail page.

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