Breeding Bird Atlas 1 Species Accounts
Number of Broods
Breeding birds begin to arrive in the first week of May, and are joined by others during the next several weeks. The redstart is also common as a migrant at this time throughout the state. Males are very territorial, and in favorable areas several may stake out claims in close proximity. They are persistent singers and will chase one another and also display by flying in wide arcs from perch to perch in a distinctive stiff-winged manner. During courtship, they may pursue the females or follow them about the territory. Constant patrolling may be required to keep out intruders, especially if the latter are unmated.
Redstart songs are extremely variable, but, as is the case with many warbler species, they can be divided into two main types, one with a loud ending note and one without. Two renditions are zee, zee, zee, zee, zwee-oo and wee-see, wee-see, wee. Both sexes have a loud chip note and a softer, thin seet note. The young have a chipping, food-begging call.
Eleven Massachusetts nests were located as follows: apple (1 nest), lilac (1 nest), Sugar Maple (1 nest), Red Maple (2 nests), Black Cherry (1 nest), unspecified deciduous trees or saplings (5 nests) (CNR, Meservey). Heights for 7 of these ranged from 8 to 20 feet and averaged 16 feet (CNR), but the range from other areas is 3 to 35 feet. Nests, constructed by the females, are neatly woven cups of grass, bark strips, plant fibers, and spiderweb lined with rootlets, fine grass, and hair. They are placed in a crotch of a tree, sapling, or bush. The normal clutch is four eggs, but two, three, and rarely five may be produced. Clutch sizes for 10 Massachusetts nests were four eggs (9 nests), five eggs (1 nest) (DKW, CNR). Two other nests were parasitized by cowbirds; one was abandoned on May 24 with a single cowbird egg, and one contained a large cowbird nestling on July 20 (CNR).
Incubation, also by the female, lasts from 12 to 14 days, and the young are fed in the nest by both parents for 8 to 10 days. When hatched, they have only sparse down. At 3 days the eyes begin to open and the wing quills show as tiny papillae, and by 8 days the birds are well feathered. Nestlings have been recorded in Massachusetts from June 10 to July 25 (Meservey, CNR). Brood sizes for 3 state nests were four young (1 nest), five young (2 nests) (EHF, CNR). Fledglings are fed for several weeks, but by the time they have attained winter plumage and appear fully grown, they are independent. At this time, aggressive interactions split up the family groups. Pairs or single adults feeding one to three fledglings have been reported in the Commonwealth from June 24 to August 6 (Meservey, CNR).
Although commonly considered to rear only one brood, in fact, some pairs do produce a second brood. Once the female has completed a new nest and clutch of eggs in early July, the burden of caring for the first-brood young falls on the male. The intensity of song may pick up again at this time, and once again aggressive encounters with intruders occur. Observations of color-marked birds showed some interesting situations. In Charlton, a female constructed a nest in a zone where the territories of two adult males overlapped. Aggressive interactions between the males were intense, and only one of them attended the female at any given time as the dominance shifted back and forth. No feedings at the nest were observed, but all three adults shared in the care of the fledglings. The female then moved well into the territory of one male and raised a second brood there with him alone (Meservey).
Adults that rear one brood are usually in heavy molt by late July. Those that are successful in producing two broods will molt in August. From late July onward, young birds, followed by adults, join the feeding flocks of Black-capped Chickadees and mixed warbler species that occur in this season. The redstart is one of the most characteristic species in these associations, with two to several individuals occurring in a high percentage of the groups. Both young and adult males occasionally sing in this season, but the songs are generally muted and incomplete.
Resident birds begin to leave on the southward flight by late August and early September, but the actual timing is difficult to determine because of the arrival of transients from farther north. Redstarts are common migrants throughout the state during September. The species occurs regularly to mid-October, with occasional stragglers noted thereafter. The wintering grounds are extensive and include Mexico, the West Indies, Central America, and northern South America. A few birds even winter in southern Florida.