Excellent post, Eric. It cannot be repeated enough how important repetition
of methodology is when conducting surveys like CBCs, migration counts, etc.
From: Vermont Birds [mailto:[log in to unmask]] On Behalf Of Eric Hynes
Sent: Thursday, January 02, 2014 10:45 AM
To: [log in to unmask]
Subject: Re: [VTBIRD] CBC Owling
Hello Vermont Birders:
To play or not to playback? That is the question. Several schools of
thought repeatedly get voiced on this subject, often
passionately/emotionally. There isn't a whole lot in the literature about
this field technique as it relates to what one might be doing on a CBC so
declaring one side "right" or "wrong" can't be substantiated. At this
point, any impacts can only be subjectively evaluated.
Human behavior in the natural world can rarely be considered benign at this
point. A number of thoughts/studies/concepts come to mind for me on this
matter which I will share in no particular order.
I believe we are into our 114th year of CBCs and there is no sign to say we
are approaching the last one so repetition of methodology is important to
compare data sets from year to year. If you have been using playback, then
you should strongly consider continuing to do so.
Many Vermont birders have probably been to Cape May or are at least aware
of it. The raptor count each fall is one of the largest concentrations on
the East Coast. Raptor enthusiasts love to debate whether the same birds
get counted more than once. It is not hard to spot a hawk from the
platform, stay on it to the tip, and then see it turn up the bay along the
shoreline and fly north again out of site. An hour later, another
Sharp-shinned Hawk approaches. Is it the same one? Nobody can say for sure.
The key to the relevance of their data set at Cape May is that they
maintain the same methodology from year to year. From a wildlife
conservation standpoint, population trends can be evaluated from their data
because they are repeating the same technique for counting each year.
There are a number of studies that demonstrate playback greatly enhances
the detection of nocturnal species versus passive listening.
One study I recall reading that specifically tried to evaluate the impacts
of playback on breeding songbirds in North America only detected measurable
changes in songbird behavior when a recording was played for *long* periods
of time, *every* day, for *weeks* straight at the same site.
A recent study from the Neotropics (I think it was in Ecuador) found that
the birds they were studying became less responsive and less vocal in the
presence of repeated playback but no impacts on breeding success were
detected. In fact, one pair fledged a brood successfully from a nest that
was built in close proximity to the audio broadcast station!
I think if there is a bottom line in all of this, they key is if you are
using playback, do sot *judiciously*! The resident owl species in Vermont
are gearing up for the breeding season now. I heard a pair of Great Horned
Owls dueting for half an hour straight the other night unsolicited. I left
before they were done. The resident owls are pretty sensitive to
"intruders" at this point. It only takes a very quick snippet usually to
get their attention. If you don't keep playing the recording for an
extended period then the owls come out as the "winners" in the exchange,
possibly bolstering their pair bond or confidence in territory defense. Who
Are the snow/ice conditions making it hard on some owls? -- Probably.
Multiple nights of extended playback might bump a bird off its territory at
a time when things are already pretty tough. But would ten seconds of
playback on one night only this winter be the straw that broke the owl's
back? -- Probably not.
I would argue that poking your head into cedars looking for roosting
Saw-whets or walking through a dense conifer stand hoping to spot a
roosting Barred or Great Horned during the day would cause a lot more
stress than a short bout of playback at night. An owl that is nervous often
flushes and burns calories flying to a new roost and avoiding the crows and
other mobbing birds.
How many Vermonters can recall when Lake Champlain regularly froze over
entirely in winter? When was the last time it did that? The range of most
resident owl species we have here in Vermont continue much farther north
than this and crusty snow is an annual event. These birds are hardier than
we often give them credit for.
Best of luck for all you CBCers for these last few counts in VT -- whatever
you decide to do! Thanks for getting out there one way or the other to
My two cents,
Field Guides Birding Tours