Saturday, June 15, 2013

Eight Amazing Facts about Bird Nests

We’ll wrap up our tour of Sonoran desert bird nests (My Favorite Bird Nests Part I and My Favorite Bird Nests Part II) with some facts I’ve learned about nesting. Several of the nests discussed here are pictured in the two posts linked above.

1. Both male and female birds build nests. With some birds, like hummers, the male has only one job: to impregnate the female. His participation is limited to the proverbial “Wham, bam, thank you, ma’am!”  Other male birds, like doves, cactus wrens and verdins, share the task of nest-building and often of raising the chicks as well.

2. The male can pick; the female can choose.Sometimes both birds participate, but have different jobs. The verdin male, for example, builds the outside shell of more than one nest and lets the female decide which to use. Then he finishes construction, while she furnishes the inside with down and other bits of fluff. With white-winged and mourning doves, the male repeatedly presents the female with sticks, and she chooses which to use and where to put them. I once spent about an hour watching a pair of white-wingeds construct a nest at the top of a support pole at Tohono Chul Park. Here’s a photo of the male holding what he apparently deemed to be a particularly excellent twig:

He's got the goods 7-25-2011 9-53-28 AM 1076x974Note: the female didn’t agree, and dropped the twig on the ground.

3. Some birds “decorate” their nests. As the photos in the posts linked above show, both hummingbirds and vireos often incorporate bits of lichen and leaves into their nests as decoration and/or camouflage. Cactus wrens often use odd found objects in their nests. I’ve seen yarn, kleenex, cellophane, and, after Christmas, even shiny bits of tinsel.

4. Birds nesting in cactus make the nest safe for their offspring. I don’t know if all cactus-nesting birds do this, but I have seen cactus wrens use their bills to methodically pluck spines from cactus where they are nesting, especially near the nest opening.

Cactus wren on cholla 10-18-2010 8-14-04 AM 1108x908A cactus wren at home in the midst of cholla spines.

5. But cactus is not always a safe environment. Cactus is a popular environment for nest-building because the cactus spines deter many predators. But not all. Several snakes, including kingsnakes, can easily climb cactus to reach and pilfer bird nests. 

6. Some birds nest INSIDE cactus. The many holes seen on the sides of saguaro cactus are produced by Gila woodpeckers (and Northern flickers). The saguaro produces a hard scab around the hole, which is then used as a nest by the woodpecker. When the woodpecker is done with its nest, other birds, including several species of owls and even house sparrows, move right in.

gorgeous saguaro 5-30-2009 4-03-19 PM 1620x2043The holes in this saguaro are most likely Gila woodpecker nests

7. Many birds do not sleep in their nests. At Tohono Chul Park, only cactus wrens and verdins roost in their nests year-round. The other birds roost on the ground, or in trees or bushes. 

8. Some birds don’t build nests. As mentioned in #6 above, many birds use an existing hole in a tree or saguaro to lay their eggs in. Other birds, like the Gambel’s quail, simply lay their eggs in a depression in the ground or even a flower pot.

Nine quail eggs 4-23-2010 10-39-44 AM 3616x2712Nine quail eggs in a flower pot at Tohono Chul Park

BONUS: If you admired the beautiful Bell’s vireo nests in yesterday’s post, link to this AMAZING VIDEO that shows a pair of vireos constructing their nest, using twigs, leaves, and spider webbing.

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