Sunday, April 22, 2012

Bluebird Trail, Week Four: First Hatch

We visited our bluebird boxes this afternoon, fairly certain that we would have our first hatchlings -- and indeed we did. In the nest with the earliest eggs, four of the five had hatched. The wonderful bluebird website says newly hatched bluebirds look like hairy shrimp, and that is right on the money. Look at their tiny wings, their sealed-over eyes and that gaping mouth. Baby birds sure are designed to show mom and dad where to deposit the food!

Four of five bluebirds hatched

Notice that the shells of the hatched eggs are already gone. In many cases the mother eats them, recapturing the calcium in them, or she may remove them from the nest. It's possible that the fifth egg will not hatch. In most cases all successful eggs will hatch within around 24 hours of each other. We'll check again in a day or so.

First-day (sometimes called Day 0) bluebird hatchlings

It was a cool week, with both  frost and a lot of rain. Cool weather can slow down incubation, and cold and wet conditions can endanger nestlings as mama comes back to the box with wet feathers. All the boxes appeared dry inside. Our BBRP county coordinator, Keith Radel, made sure all the ventilation holes in the PVC boxes were taped over securely with black electrical tape when we made our introductory rounds. This is a good practice at least for the cool springtime nesting. Bluebirds will typically have a second clutch and sometimes even a third in a season; since this year's nesting got an early start, this may well be a three-clutch season for some. The ventilation holes can be opened up for heat relief later in the season, though some bluebirders feel this is not necessary and that it is more important to minimize the chance of wet nests.

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. Calculations of incubation time are based on Sunday's early-afternoon nest check.
  1. Empty except for a little moss we put into the box to encourage a chickadee. 
  2. (Paired with #1) Empty
  3. Partial nest - little or no change 
  4. (Paired with #3) Nest about complete - little or no change
  5. Last week there were three cool eggs in this nest; this week there were five warm eggs, so incubation is anywhere from one to four days along, with hatching due in 1.5 to two weeks.
  6. (Paired with #5) Partial nest (no change)
  7. Partial nest (more developed than last week)
  8. (Paired with #7) A few strands of grass (no change)
  9. Four nestlings that look newly hatched (see photos above), and one unhatched egg. Our first hatch! We had calculated hatching to occur between Friday and Sunday.
  10. (Paired with #9) Complete nest, no eggs (no change)
  11. Discontinued  
  12. Discontinued
  13. Nest with three eggs, new this week. Eggs were cool - incubation has not begun. 
  14. Five warm eggs; female flew from box as we approached. These eggs were a day or two into incubation last week, so they are now eight or nine days into their 12-to-14-day incubation period. .
  15. Nest looks complete (increase from last week), and looks like our other bluebird nests, but a tree swallow swooped close by several times while we were near the nest box.
  16. Five warm eggs; female flew from the box when we opened it. Last week we calculated incubation to be about five days under way, so now it should be 12 days into incubation; hatching is imminent.
  17. Last week this box had a substantial nest of moss, and we assume it is a chickadee nest. There is a chickadee sleeve on this box to reduce the hole size for this smaller bird. No change this week.
  18. Paired with #17) A complete bluebird nest, in a box that was completely empty last week.
Total: Four bluebird nestlings and 19 bluebird eggs in five nests.

Follow the progress of our bluebird trail at my Bluebird Trail page.


Mary S. said...

The mouth-to-body ratio on that one bluebird is about 1-to-1. Great photos!

dAwN said...

Ha..Great Big Mouths~must be fun to monitor all those nest boxes!