[CT Birds] Some Comments on Connecticut Bird Atlas Safe Dates, Part III
stephenpaulbroker at gmail.com
Fri Apr 6 08:08:57 EDT 2018
I noted recently that the Connecticut Bird Atlas has three major components, including a breeding bird atlas, a wintering bird atlas, and a migration period atlas. We now are in the breeding bird phase of the Connecticut Bird Atlas.
Atlasing breeding birds is quite different from doing a Big Day, a Big Year, a Christmas Bird Count, or even the usual outing to see a variety of bird species. It has some similarity to doing a Summer Bird Count, as the month in which SBCs take place, June, is one of the key months for birds breeding in Connecticut. However, the focus of a breeding bird atlas is to gather any evidence of reproduction by our 175 or so bird species known to breed in the state. This effort is guided by a knowledge of so-called "safe dates” for each species, and it benefits also from some awareness of when nests are built, when egg clutches or nestlings may be found in the nest, when birds fledge, habitat preferences for each species, and of course a strong focus on bird behavior. It requires a familiarity with established and easy to use “breeding codes” for possible, probable, or confirmed breeding by each bird species.
Chris Loscalzo noted in a March 29 post to ctbirds that “we are immediately seeing the side benefits of doing the atlas as we spend more time than usual looking for nests high in trees”. During the current atlasing, we need to slow down the pace and look for any signs that birds are preparing for or carrying out nesting and raising of young. Again, the breeding codes define the evidence we use for breeding, stepping up from Possible to Probable to Confirmed breeding. Evidence of probable breeding is far more valuable than that of possible breeding, and not surprisingly confirmation of breeding is the ultimate target. This kind of atlasing often requires return visits to the same locality in pursuit of stronger evidence that a bird species is in fact breeding.
Here’s an example. Three of us have been doing a fair amount of birding in Atlas Block 80D Mount Carmel in the town of Hamden. DeWitt Allen is block leader here for the breeding season, and Gail Cameron is block leader for the winter season. I happen to live in this atlas block. On February 28, we three observed a Barred Owl flying to a tree perch in a swampy area of extensive woodland. A short time later, the owl flew again to a position out of our sight, and the bird gave its “who-cooks-for-you” call, followed by a second call of higher pitch by its apparent mate. We had found a pair of Barred Owls in territory appropriate for nesting. Over the course of the next month we made some dozen visits to this locality in search of additional evidence for breeding by this pair of Barred Owls, as well as recording all other bird species seen or heard during these trips. We saw or heard either one or both Barred Owls on four additional visits to the woodland through the month of March. Then, on March 29, the male Barred Owl was heard calling in the distance, the female launched off a tree perch and joined him for some heavy duty vocalizations, followed by her flying back to the original location and disappearing into a hollow near the top of a tall dead tree. She reappeared momentarily and flew back toward the male. Subsequent visits have confirmed that the female now is occupying that tree cavity and the male is perching nearby. Multiple times, the male has been heard calling while in view, and the female has been responding from her nest cavity.
Barred Owls are more difficult to confirm as breeders than are most species of birds. For many song birds, discovery of a nest or seeing a pair of birds on territory or carrying food or feeding young can confirm breeding during safe dates, one and done. For other, secretive species or those in challenging habitats such as marshes, more work is required to determine breeding status. In general, the best way to proceed with breeding bird atlasing is to slow down, look for behavior suggestive of breeding, make multiple trips, observe proper etiquette and give birds the space they require, and use care in applying the breeding codes. From my perspective, this is the most requiring form of birding.
In a later post, I will discuss the fuzziness and potential inaccuracy of “safe dates”.
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