Why Bird Surveys Need to be Annual

The Thought

After running the two BBS (Breeding Bird Surveys) through East-Central Indiana and analyzing the data, I had the thought WHY are bird surveys done on an annual basis? Trends in the Midwest do change but on a slower basis. And with the trouble of getting volunteers to run bird surveys why not run them for 4 or 5 years, take a 4 or 5 year break, and then repeat? That would catch the developing trends over 40-50 years and require fewer volunteers.

The Why

Then I listened to the June 6 Talking Naturally episode on BAER’S POCHARD – a Critically Endangered East Asian Duck where Charlie discusses the dramatic decline over the last 5 years of the Baer’s Pochard. The IUNC lists the Baer’s as Critically Endangered and states “It winters mainly in eastern and southern mainland China, India, Bangladesh (maximum winter total of 17 individuals in the last five years, down from 1,000–2,000 individuals [Chowdhury et al. 2012]).”

Let me state that again:

maximum winter total of 17 individuals in the last five years, down from 1,000–2,000 “.

Listening to the podcast there were 1000 recorded at two sites in 2010 and less than 300 in 2014 when there was an organized search.

Baer’s Pochard By Dick Daniels (http://carolinabirds.org/) – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=13494370

Now it was discussed the Baer’s Pochard could have wintered elsewhere for the winter but even in under surveyed China someone would have reported them. So it’s one species that definitely needs tracked annually.

But a large decrease can’t happen in the Midwest, can it?

Then I woke up and remembered the West Nile Virus and AMERICAN CROWS. If we hadn’t been tracking them on an annual basis the steep decline at the turn of the century might have not been noticed.

The composite index for the American Crow for all BBS routes in the United States. North American Breeding Bird Survey Results and Analysis 1966-2013

Let’s say the survey was run every 5 years like I was thinking. From 1995 to 2000, a 5 year break, and again from 2005-2010. The impact of the West Nile Virus would have been missed. When the survey resumed in 2005 the numbers of crows would have been half. It would have probably been noticed but would there have been the data to help track the problem?

So yes, my thought was wrong. We definitely need to take annual bird surveys.

AMCR Bird Surveys
Luckily the American Crow survived and are now almost back to previous numbers.

Luckily the numbers of American Crows didn’t drop to the point a captive breeding program was needed like the Baer’s Pochard. But if the downward trend continued the data was there to guide conservationists to take action.

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