Monday, April 09, 2007

Of Mourning Cloaks and Hummingbirds

The more I watch the life dramas that play out in my backyard the more aware I am of how interconnected life is.

Spring has come barreling across the Southern California landscape. Plants that survived the frost leafed out in record time.

The Chinese elm went from leafless to brilliant green in five days. The first hummingbird babies of the season took to the air March 23.

With her first brood of youngsters out of the nest, Alena, a one-year-old Allen’s hummingbird, began renovating a nest her mother, Hummy, built last year. This location, in a downward hanging elm branch, was not successful for her mother. Hummy’s second brood was discovered and eaten by a predator, probably another bird. (See Hummy on original nest)

When Alena chased off a group of bush tits that were eyeing the potential building materials available in this old nest, I thought she was anxious about the activity near her fledglings. I had no idea Alena had decided to build her second nest on top of her mother’s old nest.

If you look at the picture, you can see the cone-shaped bottom of the old nest. The rounded, upper half of the nest is new construction.

Enough with the background.

The real story begins with frass. That’s right, frass, the poop from insect larva. If you’ve ever grown tomatoes and had tomato worms, actually tobacco hornworms (Manduca sexta) you know what large-caterpillar frass can look like–tiny chunks of black charcoal. You may not see a tobacco hornworm or a cabbage looper but the trail of leaf damage and frass will lead a discerning eye right to the munching, pooping source.

Well, there was a lot of frass on the patio under the elm tree. Something was up there munching away on the new green leaves. Something that was numerous and rapidly getting larger.

For the past three years, western scrub jays have been infrequent visitors to our yard. West Nile virus has decimated the scrub jays, mockingbirds and American crows in our neighborhood several times since its arrival. But suddenly Saturday morning, a scrub jay was making a racket as it made it’s way through the trees.

Spiny elm caterpillars, the larva of mourning cloak butterflies (Nymphalis antiopa), were marching down out of the elm tree across our patio and up the walls of the house. Some of them were done eating and pooping and they were looking for a safe place to enter the chrysalis stage of their development. The jay had found a banquet .

While searching for roving caterpillars, the jay stumbled across another delicacy–hummingbird nestlings. From the far side of the yard a second female Allen’s hummingbird frantically voiced alarm calls. The scrub jay had found her nest in the eucalyptus tree. Alena and two other female Allen’s hummingbirds came to their cohorts aid. The foursome buzzed the jay and tried to drive it off, but it was too late. The jay consumed one youngster and flew off with the second. It was probably taking the morsel back to its own offspring.

The next morning, Alena laid an egg in her new nest.

But now the nest that seemed safe is in a dangerous place. Caterpillars continue to march down out of the elm and this morning two scrub jays were on the prowl.

The hummingbird egg sits quietly alone in the nest. Alena is not sitting on it.

Is she staying away so as to not draw attention to the nest? Has she decided to abandon the egg, realizing the nest is not in a safe location?

If the caterpillars hadn’t been so successful and their numbers so great, the jay might not have spent any time in the yard. The hummingbird nests might have been safe all summer. If Alena had made her second nest in a different tree or avoided the location that was probably raided by a jay last year, brooding her second clutch might have been as easy as the first.

Now everything is more complicated.

Life is a delicate dance. The living constantly effect each other. The weather benefits some and challenges others. No action or inaction is without effect.

1 comment:

meeyauw said...

I photographed a mourning cloak this afternoon here at home. It's not that good because it was flitting about erratically and then, of course, one of the cats chased it out of view. I have been trying to find information on the nests of the catepiller of this butterfly (I haven't re-familiarized myself with the life stages of them and am confused). I may have photographed a nest this summer. So while searching for photos, I ran across your blog and this story.

I tend to anthropomorphize, so this was quite a tragic story. I saw a crow steal a redwinged black bird baby one morning this summer and the whole beaver meadow was upset all day.

But thank you, I shall be back and am grabbing a feed to your blog.