Numerical Data on African Birds' Behaviour at the Nest: Hirundo s. smithii Leach, the Wire‐tailed Swallow

Abstract

Summary. The data, from three nests at Amani, are derived from a total of 500 hours of observations made in spells of five hours and upwards. The effect of rain on the parent birds' activity is given in detail; rain much heavier than 1 mm. per hour reduced feeding heavily, except when termites were on the wing. Brooding of eggs and young was done only by the females; their mates helped to bring food, as a rule slightly less than half the total. Incubation period 14 days; fledging 18–21. The daily percentage of time the eggs were brooded varied from 43 to 66, with no tendency to rise at lower air‐temperatures or towards the end of the incubation periods. Frequency distribution curves are given of the duration of (a) individual spells on the eggs and (b) intervals when the eggs were left uncovered. About 70 per cent, of the spells “on” lasted 2–7 minutes and 70 per cent, of the intervals “off” 2–5 minutes. Few intervals uncovered exceeded 15 minutes and none 37. Corresponding data for the fledging period are tabulated. For the first three days the young in all the nests were brooded much as the eggs had been, but after that the amount of brooding varied greatly between the nests. After a slow rise, comparatively stable feeding rates were attained at each nest during the last week of fledging. Then the average number of feeds brought in 200 minutes varied between 75 and 97 for two young and between 49 and 65 for one. The latter, which received more meals, had the shorter fledging period. There was no well‐marked diurnal rhythm in the feeding activity except that it was usually least in the early morning. The frequency distribution of length of intervals between feeds, which naturally changed with the age of the young, is tabulated. Less than 1 per cent, of the intervals exceeded 30 minutes.

Food selection and the timing of breeding of the Blue‐and‐White Swallow Notiochelidon cyanoleuca in Venezuela

“…Feeding rates of tropical swallows typically show a peak in the mid-morning or late afternoon with a lull at mid-day: this pattern is seen, for example, in the Wire-tailed Swallow Hirundo smithii (Moreau 1939), the Mangrove Swallow Iridoprocne albilinea (Ricklefs 1971) and the Pacific Swallow H. tahitica (C. J. Hails, unpubl.).…”

“…The New World martins Progne breed at the start of the wet season avoiding the heaviest rains (Snow & Snow 1964, A. K. Turner, unpubl.). In East Africa swallows and swifts lay between September and March before the main peak of rainfall in March to May but during the short rains of October and November (Moreau 1939(Moreau , 1950. In West Africa swallows breed from the late dry season to the mid-rains (Serle 1981).…”

“…In the present study the Blue-and-White Swallow bred from February to April before the peak in rainfall. A few exceptions to this occur such as the Greyrumped Swallow H. griseopyga and the White-throated Blue Swallow H. nigrita in Africa whose nests, underground or in river banks, would be flooded during heavy rains (Moreau 1950, Serle 1981.…”

“…In Costa Rica Hespenheide (1975) found that the density of flying insects is higher during cloudy but dry periods during the wet season. Skutch (1950) also suggested that the absence of northern migrants would make food more available but this is not tenable for many species (Moreau 1950, Fogden & Fogden 1979. Some, for example, start to breed well before most migrants have left (Waugh & Hails, 1983, this study).…”

“…Food shortage may delay laying (Perrins 1970) and the level and stability of the food supply during egg-laying and incubation play an important role in the timing of laying of temperate hirundines (Bryant 1975, Turner 1982a). There are also some indications, although little direct evidence, that food abundance determines timing of breeding in tropical birds (Moreau 1950, Skutch 1950, Marshall 1951, Snow & Snow 1964, Dingle & Khamala 1972, Fogden 1972, Snow 1976, Fogden & Fogden 1979.…”