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VTBIRD  April 2017

VTBIRD April 2017

Subject:

What's with woodcocks this year?

From:

Ian Worley <[log in to unmask]>

Reply-To:

Vermont Birds <[log in to unmask]>

Date:

Tue, 18 Apr 2017 09:30:37 -0400

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (135 lines)

I've been asked by several folks if woodcocks in Vermont are less
abundant this year than usual. Were the early warm spells and then the
return to winter cold and Nor'easter snows the cause of seemingly low
abundances? What can we learn from eBird data?

So I've gathered some eBird numbers from 2008 through 2017 from the
first observation of the year through the first half of April (which
includes the peak frequencies). In this case frequency of encountering
woodcocks is a better measure than the number of woodcocks found at one
time, since the average number of birds per checklist doesn't vary much.

This overview is for the entire state, so it doesn't explore data at a
county or backyard level.

*First reports* --- This year was the first year to have the first
Vermont reports in February. Among the last ten years, the latest first
report was in 2015 in the last week of March. With the exception of
anomalous 2015 all the first reports from 2012 to 2016 were in the first
week of March, whereas the first reports in 2010 and 2011 were in the
second week of March, and those of 2009 and 2008 were in the third week
of March.

Thus, there is clearly a trend toward earlier first reports of Woodcocks
in recent years.

*Peak report frequencies* --- Here are the peak weekly frequencies for
this year back to 2008. This year is one of the three lowest frequencies
during the period. The average frequencies for the last three years is
5.7; for the preceding three years is 5.7; and for the remaining four
years (2008-2011) is 7.5. So the frequency of observations in the last
six years is notably lower than in the preceding four years. And this
year is one of the lowest frequency years in the 10 year period. But
this might not be as significant as it appears because it only looks at
one two-week period (see the next topic).

2017 4.9
2016 6.1
2015 6.1
2014 5.6
2013 4.0
2012 7.4
2011 5.0
2010 6.1
2009 10.9
2008 7.8

*Frequencies for first two weeks of April* --- This is the period that
typically has the highest frequencies of observation. The average of
these frequencies is 4.8. So this year's peak period for woodcock
observations actually is not low or high, but right at the long-term
average. Moreover it is notably higher than last year, which had the
lowest frequency during peak observations for the 10 years.

2017 4.7
2016 3.7
2015 5.3
2014 5.4
2013 3.9
2012 4.3
2011 4.4
2010 5.1
2009 6.4
2008 4.9

*Average bird counts during peak frequencies* --- The average count of
birds during woodcock encounters during peak frequencies is 2.0. This
year is right in the middle and quite typical.

2017 1.9
2016 1.8
2015 1.7
2014 1.7
2013 2.0
2012 2.0
2011 2.1
2010 2.3
2009 3.1
2008 1.8

*Peak report dates* --- Peak report dates have a different meaning than
do first arrivals. Here are the weeks with the highest observation
rates. The latest was the 3rd week of April in 2008, and the earliest
are three scattered years with peaks in the last half of March. All but
one are between the 3rd week of March and the 2nd week of April, with no
trend showing.

2017 2nd week of April
2016 4th week of March
2015 2nd week of April
2014 2nd week of April
2013 2nd week of April
2012 3rd week of March
2011 1st week of April
2010 1st week of April
2009 4th week of March
2008 3rd week of April

*Time between first reports and peak frequencies* --- Long periods
between first reports and peak reports might indicate that weather and
ground conditions might have been too cold, snowy, and frozen for
survival after the first birds arrived. Here are the lengths of time:

2017 6 weeks
2016 2 weeks
2015 2 weeks
2014 5 weeks
2013 5 weeks
2012 2 weeks
2011 3 weeks
2010 3 weeks
2009 1 week
2008 4 weeks
*
**Relationship between period of time between first arrivals and peak
time vs. the frequency of woodcocks at peak* --- There is none
observable. So what happens to the very early arrivals doesn't seem to
have much effect on the overall population.

*So what's up with woodcocks this year ??* ---- Not much. It is a pretty
average year except for having the earliest arrivals in the eBird
record, which helps to create the longest period of time between the
first arrival and peak frequency. If compared with last year, there are
more woodcocks being reported this year than last by 27%.

Here at my location on the southern end of Snake Mountain in Cornwall, I
do morning and evening observations for woodcocks beginning in early
February. After a couple of remarkably early birds in February, there
was a long, long wait until they began to show up in late March. For
the past three weeks they have been continuously present as normal,
though from my observation location it is difficult to monitor numbers.

Best spring wishes,

Ian

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