Friday, December 9, 2011

Friday Roundup-Arctic Owls in the United States

1. Snowy Owls Venture South. I would venture a guess that many people in the United States would say the closest they will ever get to a Snowy Owl, Nyctea scandiaca, is a Harry Potter Movie. They might be surprised.

It has long been known that Snowy Owls from northern Canada periodically venture far south (here's one filmed in Tennessee in 2009). Last month, a Snowy Owl was photographed outside of New York City (click here to view the details and fantastic photographs). Their appearances in the United States tend to take place during the winter months. Perhaps as a result, many ornithologists (scientists who study birds) believed that when populations of small mammals (like voles or lemmings, which owls love to eat) decreased to very low levels, Snowy Owls migrated south in large numbers to find more food.

This idea persisted for a long time. Before I started investigating the NYC owl for this blog, I probably would have repeated that story to you. But, there is actually little evidence to suggest that Snowy Owls head south because of changes in prey populations. It is probably more accurate to think of Snowy Owls simply as a migratory species, just like many of the other bird species that can be found along the east coast of the United States. Many songbirds, for example, breed in the northeastern United States but spend their winters in Central and South America. Snowy Owls probably do something similar, they are just starting from further north. When you come from northern Canada, I suppose a New York winter feels relatively mild, there's no need to head all the way down to South America.

Two weeks ago, a pair of Great Horned Owls, Bubo virginianus, took up residence in some dead trees along a pond in my yard. At night their mournful hooting gave voice to the night. I only ever saw one, the owl was a dark silhouette against the sky in the last few moments of sunlight. After four nights, they vanished and I have not heard them since.

A Ctenosaur Surveying His Territory
2. Here Be Dragons. The largest lizards I have ever seen were the giant ctenosaurs (aka spiny-tailed iguanas) of Palo Verde, Costa Rica. Although equipped with an impressive set of teeth, they are largely herbivorous and timid creatures.

Those words have not often been used to describe the world's largest lizard, the Komodo Dragon, Varanus komodensis. Early European explorers feared encountering dragons during their expeditions, but their fears were generally unfounded unless they happen to be sailing through Indonesia, where they might encounter a the famed dragons of Komodo. These lizards are famed for their hunting strategies, which allow them to take down mammals much larger than themselves. A wild creature that most only know from books or nature programs on television, Komodo Dragons are the epitome of The Wild.

In his blog, Laelaps, Brian Switek writes about how Komodo Dragons became known to most of the world and describes early attempts to keep these incredible creatures in captivity. In the course of telling the story of the Komodo Dragon, Brian offers some commentary on the role of zoos; one cannot help but wonder whether observing a majestic creature in an enclosure can be compared to the experience of knowing you're sharing the landscape with one (or many).



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Much of what I write is based on my experience in the field, however I also rely on the research of others. Citations of some relevant scientific articles are included below.

P. Kerlinger, M. R. Lein, & B. J. Sevick (1985). Distribution and population fluctuations of wintering snowy owls (Nyctea scandiaca) in North America Canadian Journal of Zoology, 63, 1829-1834

1 comment:

Shelly Cox said...

I live in NW Missouri, and in the past week two snowy owls have been sighted at Smithville Lake just southeast of me by about an hour. There are constant reports coming of the exact whereabouts so people can go see them. I plan to try and locate them this weekend. I have not seen a snowy since I was little girl, that time at Squaw Creek NWR.