It's a fly-eat-fly world

This big bristly robber fly has captured a smaller green blowfly. 

Urban wildlife is not all butterflies and baby birds. I found this pair of flies on one of the rustic log fences of the Shakespeare Garden in Central Park.

The robber fly is a female. We can tell by her scary looking sword-shaped “tail” – it’s really an egg laying apparatus called an ovipositor.

Like other robber flies, she is a predator. She has killed the blowfly. After capture, she pierces her victims with a needle-like mouth and injects deadly saliva that paralyzes and digests. Then she sucks out their liquefied insides like bubble tea. The struggle was all over by the time I got there; she was lingering over her meal.

There are many kinds of robber flies -- over 5000 species worldwide, about 1000 species in North America, and about 100 in the Eastern United States. The one in the picture is in the genus Efferia. Robber flies eat other flies, bees, wasps, grasshoppers, dragonflies and spiders. Prey larger than themselves does not deter them.

Robber flies have bristly mustaches that help protect their eyes and faces when their victims put up a fight. 

We may find robber flies disturbing, but they are considered beneficial because of the insects they eat. Just don’t try to pick one up or it might poke you with its needle-like mouth. 


There is more information about urban insects in my book, A Field Guide to Urban Wildlife of North America, which will be published by Stackpole Books in spring 2011. 

New Bird!

This immature northern cardinal, Cardinalis cardinalis, showed up on the porch this week. It looks like its dad -- crested and thick-billed -- but it has not yet acquired its adult colors.

This bright male is probably the father. He has been visiting our porch for seeds and peanuts for a few years, especially during winter when food is hard to find and for the last few weeks while he has been feeding his new family. 

The female cardinal is mainly brown like the immature, but she has a bright orange bill and red highlights.

During mating season males often feed females, passing a bit of food from his beak to hers. Cardinal form pairs in spring, when males define and begin to defend territories – like the garden behind our building.

Females build bowl-shaped nests in privet and rose bushes, briars, lilacs, honeysuckle, hardwood saplings, young evergreens, and shrubs. The nest is usually placed between four and five feet from the ground. They build with weed stems, small flexible twigs, bark strips, grass, vines, rootlets, leaves and paper.

Cardinal eggs are dotted, spotted, and blotched with brown on a grayish-white background. Females incubate while males bring food. It's a perilous business; many eggs are lost to cats, blue jays, nest collapse, wind, and other accidents. But cardinals are persistent. It they lose a nest, they build another.

When a clutch of eggs hatches, the female often starts a new nest while the father takes over raising the hatchlings. Two nests mean twice as many trips to my window! Over the last month, the male cardinal has been visiting a few times a day; he sits on the sill looking in, chipping loudly, and waving his wings for attention.

Cardinals are famous for using the same feeding and nesting spots year after year. They can live for more than ten years. We have lots of visits to look forward to!

There is more information about urban birds in my book, A Field Guide to Urban Wildlife of North America, which will be published by Stackpole Books in spring 2011. 

Mallards

Mallard ducklings, Anas platyrhynchos.

A bundle of fuzzy ducklings is probably not the first thing that you picture when you think of New York City's Central Park. This group was resting in the grass by a pond about half a block from the Plaza Hotel.

The mother mallard kept an eye on me while I took photos. 



The ducklings' father may have been among the group of males loafing on the muddy banks of the pond, but he has no responsibility for rearing the youngsters. It's all up to her.

The male mallard has a shiny green head, chestnut breast, silvery wing feathers, and yellow bill.


Surprisingly -- like that guy in the Enzyte commercial -- male ducks have sexual secrets that people (mainly ornithologists) talk about.

To begin with, male ducks, along with their pond mates the geese and swans and a small selection of other kinds of birds, have penises. Most birds do not; they just have single multi-function openings called cloacae that can eliminate waste or transfer sperm at need. Ducks keep their penises discretely tucked inside their bodies when not in use.

But ducks not only have penises -- some of them are famous for having extravagant penises shaped like corkscrews and of disproportionate length. Even the New York Times has written about the Argentine Lake Duck's body-length penis. Scholarly publications describe that duck's sexual behavior as promiscuous and boisterous.

And not only that! During breeding season male mallards often chase females (other than their mates) in pursuit of forced copulations that some ornithologists call "duck rape."

We tend not to pay too much attention to mallard ducks because they are so common. Maybe we should be keeping an eye on them.

There is more information about urban birds in my book, A Field Guide to Urban Wildlife of North America, which will be published by Stackpole Books in spring 2011. 

Sycamore tussock moth caterpillars

Sycamore tussock moth caterpillars, Halysidota harrisii, are falling out of the trees in New York City this week. This one is crossing paths with a tiny red spider mite. 


I keep finding sycamore tussock moth caterpillars on low stone walls in Manhattan’s Central Park and on the iron fences that surround the lawns of the American Museum of Natural History. 

The caterpillars are covered with white hairs. They have four orange tufts and four white tufts on the front end and a pair of white tufts on the rear. They will eventually grow to be relatively unremarkable yellow moths with pale bands on their wings.

Each time I find one of the caterpillars I look up and see either a London plane tree or an American sycamore – their host plants.

 American sycamores and London plane trees are easily recognized by bark that peels off to leave puzzle-piece patterns of green, cream, and brown on trunk and branches. 

Like many insects, sycamore tussock moth caterpillars eat just a few related plants -- sycamores and plane trees -- and have ended up being named after their food. They eat the soft green leaf tissue and leave behind lacy leaf skeletons made of stems and veins.

Sycamore tussock moths spend the winter in cocoons on host trees. Adult moths emerge in spring. They mate and then lay eggs under leaves and on bark. The eggs soon hatch into a profusion of fancy white caterpillars. By June,  there are so many caterpillars that we notice them falling out of the trees and walking along fences.

The caterpillars we are seeing in Manhattan now will soon make cocoons. They’ll emerge as adult moths in late July and August to mate and lay eggs that will hatch into a second wave of caterpillars at summer’s end. Those caterpillars will make cocoons in September or October and spend the winter inside them -- emerging as adults next spring to begin the cycle again.

There is more information about urban moths and butterflies in my book, A Field Guide to Urban Wildlife of North America, which will be published by Stackpole Books in spring 2011.