Tree Swallow

Status Common in summer. Breeds. Tree Swallows are the first swallows to arrive in spring (average 6 April, earliest 22 March), but a dying bird in Halifax on 3 March 1968 and two lively ones at Cape Sable on 28 February 1976 clearly were not normal migrants. In summer they are widespread and common in towns and along watercourses. Local birds and transients form large gatherings from mid-August through early September. A few remain much later, and last sightings are routine in November (average 6 November, latest 27 November). Birds seen after 11 December four times since 1969, the latest sightings being on the Halifax East Christmas Bird Count on 20 December 1969 (seven birds) and on the count at Port L'Hebert, Shelburne County, on 20 December 1981 (two birds), had probably been brought back north by storms.

Description Length: 13-15 cm. Adult males: Upperparts iridescent blue to green; underparts pure white; tail slightly notched. Adult females: Not infrequently, lack the iridescence on back which may be dull olive-brown. Immatures: Upperparts dull olive brown.

Breeding Nest: Usually in a hollow tree or man-made nest box. It is composed of coarse vegetable matter with a profuse lining of feathers, placed so they curl up over the eggs. In selecting feathers for nest lining, the bird refuses black or even dark ones, insisting that they be white or light gray, at least that has been my experience. If feeding conditions are particularly favourable over a terrain without conventional nest sites (such as is the situation on one of the Mud Islands off the coast of Yarmouth), it will nest on the ground under a flat stone or in a hole it excavates in the ground (Langille 1892).

Eggs: 4-6, usually 5; white. Laying normally commences at the beginning of June. Usually a single brood is raised, but there are exceptions. Harold F. Tufts observed a pair raising two broods in his garden at Port Mouton, Queens County, during summer 1960. The first young bird of a brood of five left the nest during the last days of June, as is normal. Within a few days a parent was seen carrying nesting material to another box nearby, which a brood of four eventually left on July 31. Dr. Tufts mentioned that this had not been the first time a pair of Tree Swallows had reared two families in one season on his premises.

An unusual incident occurred in 1953. On 7 July the last of five young left one of my nest boxes, but a parent bird continued to enter and leave repeatedly thereafter. On the morning of 9 July, I opened the box and found two newly hatched young. They were cared for normally and flew on 27 and 31 July. The only tenable explanation is that the female (or another) laid the two eggs while brooding was in progress, the necessary warmth for successful incubation being provided by the parent and young at night and by the fledglings during the daytime. It was noted that only one bird, presumably the female, cared for the young from 9 to 31 July. Why these eggs had not been trampled and broken during the development of five husky young swallows remains a mystery.

Range Breeds from north-central Alaska to Newfoundland and, in the east, south to North Carolina. Winters on the Gulf Coast, in northern Mexico south to Guatemala, and occasionally north to Massachusetts and New York State.

Remarks The practice of providing nest boxes for these birds has become prevalent. This is unquestionably a boon to the swallows, but these boxes are also coveted by House Sparrows, and competition is often very keen, with the ruffians usually taking over. There are several ways to assist the swallows at such times without resorting to the use of firearms. It is helpful if the entrance hole is elliptical, the vertical measurement being not over 2.4 cm. The horizontal measurement is not important. If made 5-7.5 cm wide it will provide sufficient elbow-room for several little yellow lined mouths, instead of the usual one, to compete for the food brought during the final days of their confinement. A hole this size discourages the sparrows but is not totally effective. However, if the hole is any smaller the swallows have difficulty entering. So two other suggestions are offered. Suspend the box close to a window, close enough that it is within reach when the window is opened. If that is not feasible, hang it 1.5-2 m off the ground, being careful not to place it where a cat can reach it.

It is always pleasing to have the swallows come back in early spring, but an early arrival does not always work well for the swallows, as happened in April 1940. They were first seen on the 18th, when the weather was delightful. On the 21st it turned cold and snow began falling and continued to do so, intermittently, through the 23rd. Over 30 cm of snow covered much of the ground and temperatures slightly below freezing prevailed. At Gaspereau, Kings County, 100 or more Tree Swallows were seen near a sheltered embankment by the river on the 23rd; those still alive sat dejectedly on the trees, their wings drooping, many so weak from starvation and cold that handling was possible, while others were strewn about on the snow either dead or too weak to fly. Other migrants arrived later but the species appeared to be reduced in numbers that summer.