The summer of 2018 proved to be a really great start for the atlas, but whenever we present last year’s data we are constantly pointing out that comparisons to the first atlas need to be made with care. In part, we make these cautions because the data are still being reviewed to ensure we’ve made no errors. But, the main reason is simply that the historic data come from five years of field work, not just one.
The two parid species – black-capped chickadee and tufted titmouse – nicely illustrate why we need to be so careful. The comparison maps below compare data from the 1980s atlas to those from 2018.
Breeding atlas reports of black-capped chickadee in Connecticut during the 1980s (left) and during 2018 (right).
Breeding atlas reports of tufted titmouse in Connecticut during the 1980s (left) and during 2018 (right).
Superficially, these comparisons suggest that both species have declined. We know, however, from the USGS Breeding Bird Survey – the best long-term trend data for North American birds – that this is not the case. Black-capped chickadees have stable populations in the northeast, while tufted titmice have been steadily increasing since the 1960s.
The differences in these maps must, therefore, reflect the difference in survey effort. That we have not yet achieved the equivalent of 5 years of coverage is, of course, unsurprising. But, with only three years to complete field work for the current atlas, it’s clear that there’s a long way to go.
Fortunately, we are already within the safe dates for both chickadees and titmice, so any observations with breeding codes should be reported. If you have not yet found these species in your block, and you see one in appropriate breeding habitat, then the H code should be used. If they are singing, then use code S instead (but be careful because not all vocalizations count as singing – the characteristic dee-dee-dee call of a chickadee is not a song).
Nest building may also have begun, so watch for birds going back and forth to the same tree, especially if it is a dead snag, as you may see a bird excavating a nest hole (code NB). With fair weather forecast for the weekend, it would be great to see how many of the blanks on the current atlas maps for these species we can fill this week.
Black-capped chickadee excavating a nest hole in a dead maple stump in Storrs, 7th April 2018.