A(WASH) IN HABITAT (SOURCES AND SINKS)
“We saw a car go by early in the AM and figured it was related to the bird count--either that or someone was scoping our place for a pre-Christmas burglary!” That was an email I received a couple of days ago.
How about you? Last Sunday, December 18, did you see carloads of strangers cruising your neighborhood? In the pre-dawn hours, did a car race by, only to stop with lights off, while the passengers quietly disembarked?
December 18 was, indeed, the 117th annual Christmas Bird Count organized by the National Audubon Society. Grand Junction has been a participant since the 1950s. During the daylight hours, teams are cruising the valley within a 15-mile diameter circle centered at H and 24 roads. These teams count every bird they can see. Over the decades a lot can be learned from these data—pheasants disappearing, and Eurasian Collared Doves becoming one of the most abundant birds are two examples.
For me, it is all about Western Screech-Owls. I developed routes for 18 teams that were out in the pre-dawn driving to selected locations to play a call and see if an owl appeared. Although, the 75 we found this year was a significant decrease from the past two years, it was the third highest number of this owl ever reported. Yes, Grand Junction is number 1 in something—Western Screech-owls! (http://www.gjsentinel.com/blogs/birds_and_more/entry/owlish-onslaught)
(Western Screech-owls rarely use a box like this, but last Sunday this one was sunning itself making counting easy.)
One of the volunteers helping me set up the calling routes a couple of days before the count commented to me, “Have you noticed most of the stops are near washes?” Well, I certainly had, but when I looked on a map, it was more striking than I had realized.
Many years ago, the great conservationist, Aldo Leopold, suggested that every farmer should leave the last row of his field for wildlife. That never happened. In the conservative part of the Midwest where I grew up, it was more common for adjacent farmers to wait for the other guy to plow first, so they could follow and take part of a row from the neighbor’s field. There was no such thing as a wildlife buffer. It might be the same here, except we, from a wildlife perspective, are blessed with washes. Some may call them canals, drainage ditches or arroyos, but without them, there would be only a fraction of the wildlife that we are accustomed to in this valley.
After I compared our calling locations with a map showing the washes, I immediately thought of the flat areas of Western Kansas where crops are grown property-boundary to property-boundary as I described near my hometown. There’s not much wildlife. Where would animals and birds hide? Where would they breed? That’s the problem.
(Grand Valley washes are both home and highway for our wildlife. Photo courtesy of LeeGelattPhotography.com)
Habitat is often broadly characterized as “source,” that is, where wildlife may successfully breed, or “sink,” where those individuals in excess of what the source area can support live, but with a lower rate of survival and breeding success. Consider that fledgling Western Screech-Owls often flutter from the nest to low shrubs and even the ground for a day or two. If their nest site was urban/suburban, they are susceptible to cats, dogs and cars. If the nest is near one of the broad washes, despite the presence of some of the same predators and more, there is more cover, and hunting was probably better for their parents such that the fledglings might be just a bit more fit-for-survival.
These extra surviving fledglings from the wash have to find their own place, and may be the ones you see in your backyard in town or in an owl box near Lincoln Park or East Middle School. We are happy to see them in our schools and parks, but we suspect their breeding success is limited. These are probably “sink” habitats.
This year may have revealed to us a local contraction of the Western Screech-Owl population. One year of data is not a scientific record, but I can speculate. My view of the data shows a decrease in owls within the more urbanized/suburbanized area. Western Screech-owls do not live long, and if their prey base (think mice in the winter) goes through a lower population cycle, fewer owls survive—especially fledglings. The survivors will take the best habitat—along the drainages—and we will see fewer in town.
Is that what happened? Maybe. Only more data will tell us for sure. We can say this, however, if you live near a wash, don’t burn it. Don’t spray it. That’s the most important habitat in the valley. And, next year, come join us. Your cup of organic coffee will taste even better after an early morning listening and looking for owls.
(It isn’t too late to join a local Christmas Bird Count. The Grand Mesa Count occurs every year on January 1. If you’d like to join us, check the website for details www.audubongv.org)
This post provided by Nic Korte, Grand Valley Audubon Society. Send questions/comments to email@example.com]To learn more and to participate in the activities of Grand Valley Audubon, please see our website at audubongv.org and “like” us on Facebook!]