The month of April is the start of the nesting season for bluebirds and tree swallows at Veasy Memorial Park (VMP). Since both species build their nests inside cavities, nest boxes have been placed throughout the VMP field to accommodate the nesting needs of these birds. Though they build nests inside natural cavities such as old woodpecker-excavated cavities, these birds will readily accept man-made nest boxes, especially, when placed in open areas such as the field at VMP. Currently, there are 17 nest boxes at VMP and another box in Meadow Pond Reservation, which is located across the street from VMP. The VMP nest box program began in the spring of 2005.
Often, April and even May at the park can present cool and wet weather that make nesting challenging. Bluebirds will attempt nesting early in April and sometimes in late March while tree swallows are somewhat later starters. Fortunately for this year, April was relatively mild and our nesting birds got off to a good start. During April, there were three bluebird and one tree swallow nests with clutches of eggs. Two of the bluebird nests produced hatchlings before the month ended! Definitely, this is an early appearance of bluebird nestlings.
The nest boxes are regularly monitored for bird development and box maintenance. Important
developmental information includes the date that the first egg is laid, the hatch date and the date the nestlings fledged, or leave the nest box. Monitoring can be complicated by the fact that the female will lay only one egg per day and might not begin incubating the clutch of eggs up to a week after the last egg is deposited in the nest. The egg laying period is followed by the incubation, hatchling, nestling and fledging periods. Once this cycle is completed, a new generation of independent offspring is produced.
Incubation can last from 12 to 16 days for both bluebirds and tree swallows. The young usually all hatch within two days of each other, and both species are altricial, that is the hatchlings are immobile, downless and naked, and their eyes closed for several days after hatching. They rely completely on their parents for survival. In contrast, turkeys are precocial where the hatchlings are mobile, downy, and follow their mother who shows what to eat. Once they hatch, bluebirds and tree swallows will need an additional 15 to 20 days to fully develop and fledge (able to leave the nest box).
With some simple arithmetic, you can see that it takes about 34 to 43 days to produce a self-sufficient new generation of offspring. In our region of the country, breeding bluebirds sometimes produce two broods of offspring, though tree swallows seem content with a single brood, each season. Imagine a breeding pair of bluebirds could produce two generations of bluebirds, and be grandparents at the end of their second breeding season.
Maybe that is the reason they don’t live for many years – about 2 to 5 years on average.
Richard Lombard … May 2010
Winter Nesting Box
Photo by D. Blackwell
