Who builds the nest?

First of all, it is amazing that a little bird that hatches out of an egg one June morning, can the next year build a nest of its own that is a typical specimen for its species (with no training even). Secondly, it is interesting that often it is only the female that builds it. The male presumably is above such domestic endeavors.

But not in all species. I'm not positive (and because this is a blog I'm not required to verify it), but I believe that the vireos and possibly other groups engage in dual-sex nest building. (Go check your Birders Handbook and post the answer for me below.) I seem to remember watching two blue-headed vireos both collecting nesting material together once somewhere near a hemlock-lined stream in Pennsylvania. Maybe it was a dream.

Now for the point of my story. Today I witnessed a common thing: a female bluebird making repeated trips to a nest box with a mouthful of nesting materials (grasses, pine needles, etc.). But the interesting thing was that the bright blue male followed her every step of the way, but did none of the work. He would fly with her to a spot several hundred meters away to collect stuff (staying within a few meters). Then he would fly all the way back to the nest while she put it in the box. While she was in there, he would perch on top and sometimes come down to look in.

This has two potential explanations, as far as I can tell: 1) he was guarding her against being cuckolded by rogue males (as she was likely approaching fertility at this point), and 2) well there is no 2. But it is also possible that this "male accompaniment" is some sort of transition between "male doesn't help at all" and "male helps build nest." No proof, but why not. I'm pretty sure there are also cases in which the "male helps a little bit."

Nestlings by the numbers

After my last post, I started reexamining my pics of Acadian flycatcher chicks to see if I could actually identify the fuzzy tufts that I only recently found out have names. I realized that many of them are actually pretty obvious (see below for key), and I also realized that the close-cropped white fuzz of Acadians make them a pretty good study-species for the aspiring fuzz-identifier (fuzzer?). Compare, for example, the wispy, hard-to-differentiate fuzz of baby grasshopper sparrows. And besides being funny-looking (I especially like the "occipital" patch - #2 - for it's jauntiness), these humble fuzz-patches can even tell an evolutionary tale. If I remember correctly, the Acadian is the only Empidonax to have white rather than tan fuzz, one of several things that make it an outsider in its group (nest structure, range, and habitat also come to mind). Connect the numbered tufts to reveal a hidden picture!

Baby birds are strange

Actual scientific drawing from Saunders (1956)

Very strange indeed. It seems like the random tufts of fuzz on newly hatched chicks are just for decoration. What other purpose could they serve? Warmth? It does look warm, but there's not enough of it. There are apparently names for each little patch, too. I came across a 1956 paper in the journal Bird Banding (by Aretas Saunders) that describes the fuzz from several species, and gives names to each fuzz patch. I don't necessarily see the corresponding patches on the nestling photos that I have (see below), but maybe it varies by species (the drawing is of a chipping sparrow). Maybe I should actually read the article. Here are the patches (refer to numbers on the cute yet scientific drawing above):

1. coronal      } capital

2. occipital     }  tract

3. dorsal
4. humeral
5. femoral
6. caudal
7. secondary   }  alar

8. primary       }  tract
9. crural
10. abdominal  } abdominal
11. lateral        }     tract

Here are some pics of alien nestlings from my files:

 Acadian flycatcher

eastern meadowlark

blue grosbeak

 grasshopper sparrow

field sparrow

Lit cited

Saunders, A. A. 1956. Descriptions of newly-hatched passerine birds. Bird Banding 27:121-128.

Good books

Baby Bird Portraits: Watercolors in the Field Museum

They grow up fast

Once upon a time, I was an Acadian flycatcher nest-finder.

A few nests (out of around 150) were really low and easy to photograph. These were fun to follow, and made you realize how amazingly fast birds grow up: from egg to fully feathered fledgling in about 14 days. (This is actually nothing compared with grasshopper sparrows and their grass-dwelling ilk, which fledge in only 8-9 days!)

Here is one Acadian flycatcher nest I documented (almost) daily...

Day 0 - Hatch day. Tiny, fuzzy, and blind.

Day 0 - Later in the day. Last egg hatched, but looks a little runty.

Day 1 - Skin has gotten a little less orange and more pink. Little Runty's fuzz has dried, but he is still noticeably smaller.

Day 2 - Tiny pin feather pins visible beneath skin on back and head. Little Runty is not looking too good.

Day 3 - Pin feathers have broken the skin. Little Runty looks larger, but is dead or nearing death.

Day 4 - Pin feathers nicely developed. Little Runty seems to have died (he's visible underneath bottom nestling).

Day 5 - Feather plumes beginning to emerge from pin feather sheaths. Little Runty appears to be gone - removed by parents?

Day 6 - Feathers covering up much of the skin between feather tracts.

Day 7 - Looking rather furry. Just a little skin visible.
Day 8 - No skin visible. All feathered, but still a little pin-feathery looking. And more golden colored than gray (due to feather tips).

Day 10 - Fully feathered, gray plumage with cream-colored wing bars. Alert and getting wary of visitors. Only 4 days left until fledging, and 2 days before they can jump ship if disturbed. Sadly these guys were eaten by predators later this day or overnight.

Day 11 - Here is another nest with 3 nestlings, 11 days old. Getting pretty crowded! Only three more days left like this.


I don't have any photos of older nests because they get pretty skittish after 10 days. But here are some of adults to complete the cycle: