Birds of North America Online says this about 2nd broods in White-breasted Nuthathches (WBNU):
Neither renesting after nest failure, nor more than one brood per season, reported. The dates in the first CO Breeding Bird Atlas show late nesting not to be uncommon: nest building, as late as 7/10; nest with young, 7/24. Don't dates that late, especially in a species that starts to nest early in the season, suggest 2nd broods and/or renesting? This question arose for me while monitoring nest boxes on our 39+ acres of pinyon/juniper habitat at about 7,000' 18 miles east of Salida. WBNUs are the earliest nesting species of the 7 that have used our boxes, with first eggs usually in early to mid-April. Starting a bit late this year (early May), a pair of WBNUs fledged a brood of 4 on 6/6. On 6/11, in a nest box about 30 yards from the original box, 2 small, plain eggs appeared in an abandoned Juniper Titmouse nest. Since Violet-green Swallows were starting to nest at that time, and they not infrequently take over an earlier nest after that group has fledged, I chalked it up to a swallow nest. However, as I headed to check the box on 7/3, a WBNU went into the box briefly and hopped back out. Sure enough, when I opened the box--2 WBNU nestlings, about 3 days old. I have also seen likely renesting after a chipmunk depredated a WBNU nest in 2009--in the same box, 7 days after the nest was depredated, a full clutch was laid again. Of course, without banded birds, one cannot be certain that either of these instances was a 2nd attempt by the same pair. But both seem rather likely. I typically assume that rare events don't happen to me. Does anyone know how common 2nd broods are among WBNUs in CO? Tina Mitchell Coaldale, CO -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/cobirds?hl=en.
