Tuesday, April 26, 2016

On the proliferation of Eurasian Collared-Doves in Orange County

A Eurasian Collared-Dove in Anaheim on Sunday

Orange County is different every time I visit. New housing developments encroach ever deeper into the hills. Trees are "trimmed" (read: mutilated) further and further into oblivion. And there are always more Eurasian Collared-Doves. 

This is going to make me sound old, but here goes. I remember when things were different. There was a time when Eurasian Collared-Doves were not common in Orange County. When I moved here in 2007, they were downright difficult to find. Over the last few years, they've become commonplace. In fact, I saw one the other day a mere mile from my house. I predict that I will soon add this species to my almost legendary Hood List. 

This expansion is hardly surprising, given hemispheric trends for this species. Want a good laugh? Check out the dove's map in the original Sibley. It is rapidly expanding west, east, north, south. "Collared-Dove," I told Joel as we crossed the Michigan-Indiana state line in early January, "Will probably be the first new species we see." Sure enough, dozens greeted us at a rest stop in central Illinois. Their coos serenaded us at every piss stop across the country--Missouri, Oklahoma, New Mexico, Arizona, California. Then we flew to Mexico--and there, too, the streets echoed with their calls. And they were verminous in the Dominican Republic. I just can't get away from them.

Let us consider their conquest of Orange County. First, courtesy of eBird, here is an overview of their North American range.
This next map shows Eurasian Collared-Dove records in southern California up to the year 2005.Very sparse in Orange County, with greater numbers up north towards Los Angeles.
Fast forward to 2011. Things are filling in slowly in Orange County, though the species seems to be increasing rapidly up north in Los Angeles County and in western Riverside County.
And finally, all records up to the present (red pins indicate records from the past month.) Explosion. Blietzkrieg. The Collared-Dove has conquered Orange County. 
Using eBird to track the expansion of this species may be deceptive, since the dove's invasion of Orange County coincided (or slightly preceded) the widespread adoption of eBird by birders. Fortunately, Christmas Bird Count data for Orange County is readily available online (thanks, Sea and Sage Audubon). The data support my general impressions that (1) Eurasian Collared-Doves first began appearing in Orange County in roughly 2005, and (2) that the population has rapidly increased since then--particularly since about 2010.

In past decades, a different dove reigned in Orange County--the Spotted Dove. They were abundant through the 90's (the 1990 Coastal CBC recorded upwards of 250), but their population crashed. The last surviving Spotted Doves overlapped with the pioneering Collared-Doves in the early 2000's. It is fun to speculate about the rise and fall of two nonnative doves in Orange County--did the Collars drive out the Spots? At least in the context of Orange County, I find this hard to believe--by the time the Collared-Doves showed up, the Spotted Doves had already been gone for years. But, who knows? 

And will the Eurasian Collared-Dove share the Spotted Dove's fate in Orange County? I doubt it--I foresee the dove expanding further, saturating the county--nay, the country-- interminably.

1 comment:

Quentin Brown said...

That was a very interesting article and thanks for sharing. Here in North Vancouver, Canada I noticed, for the first time in several years, no collared-doves singing in our neighbourhood. I heard from a few others who had the same experience. Collared-doves are not far away, closer to the water in industrial areas, they are common. So I looked at ebird maps. The map from the past ten years shows sightings from above and below Highway One. Above the highway, it's residential and higher in elevation. Below the highway, it's a mixture of residential and industrial and low in elevation. Then I checked the current year map. Not a single sighting above Highway One. It seems as if Collared-doves have retracted their range, at least in this neck of the woods.
Quentin Brown