Breeding season of Madagascar Birds - Rand

The aim of our work in Madagascar was the collection of a series of bird skins. We were continually moving, seldom spending more than a month in any one place or more than a few months in any part of the island. With the restriction of a species to one or another part of the island, it was impossible to follow the activities of any but the most widespread species throughout the year. The different climatic conditions over this island, chiefly the duration of the rainy season, probably imposes different limits on the extent of the breeding season of the same widespread species in different parts of Madagascar. Our data can show only the amount of breeding activity in certain parts of the island for limited periods and so enable us to form an idea of the general breeding season over the whole island.

Besides the nests found, birds which were found upon dissection to have their gonads enlarged were considered as indicators of the time of breeding. When fledgling birds were found the probable month of egg-laying was estimated to give the approximate time of breeding (this accounts for the breeding records we have for a locality during the months when we were not there).

We found that most of the woodland species were beginning to breed in August and September in the Humid East, before the heavy rains.

During October and December most of the birds were breeding in the north and northwest and southwest. In January, February, and March, birds were still breeding in the region about Soalala in the west when the rains were still frequent; but in the southwest where little rain fell during this period, the breeding season was over for most species.

We were not in the field much during April, the end of the rainy season, but a few birds appeared to be still breeding in the area about Majunga (west) during this month, and many of the water birds at Andreba (east) had apparently bred during April also. During May, in the dry season, few birds were breeding on the central plateau at Manjakatompo, none of the forest birds were breeding at Fanovana (east), and very few in the northeast. During June, i.e. the dry season, in the southeast, the northeast and the west, few forest birds were breeding.

From this evidence we can assume that the breeding season for forest birds in general started a month or two before the rainy season, i.e. in the latter part of August and September in the Humid East, continued until March or April, the end of the rainy season in the western savanna, and lasted not much beyond December in the arid part of the Subdesert, where little rain fell at any season of the year.

The birds of the open ground, brushlands, and marshes seem much less restricted to any one season and some of them, such as Foudia madagascariensis, Mirafra hova, Cisticola cherina, and Eremialector personatus, seem to breed throughout the year, but it is improbable that they do so in all localities. Local conditions probably affect this.

Thus Foudia madagascariensis was not breeding over the greater part of the arid country about Ampotaka in March but I found one nest in the rank vegetation along the river. In the souitheast in June and July, Streptopelia p. picturata collected in the forest showed no signs of breeding, but some of them collected in the brushland were breeding at this time.

Also, while some individuals may be breeding, others in the same habitat may not be doing so. At Tananarive in May, I found a nest of Mirafra hova with eggs in it and saw numbers of these birds giving their flight song and at the same time collected many other specimens of the same species that showed no indication of breeding.

Some marsh species were found breeding in April and May at Lac Alaotra (east) and in December at Lac Iotry (southwest), but we lack data for determining whether they breed during the whole year in some localities or whether they have different breeding seasons in different parts of the island. The latter seems improbable.

The following is a summary of the breeding activities of the various biotic districts:

-        SOUTHERN PART OF THE HUMID EAST:

Observations made from June to October. In June very few birds were breeding. In July, a few open-ground birds and in August some woodland birds began to breed. In September and October many of the birds were breeding.

-        CENTRAL PART OF THE HUMID EAST:

Observations made from April to June. In April none of the birds of the forest were breeding at Fanovana; in May and June, at Andreba, many of the water birds were breeding or had bred but a short time before.

-        NORTHERN PART OF THE HUMID EAST:

Observations made from May to September. In May, June, and July few of the birds were found breeding; in the latter part of August and the first part of September, many forest birds were beginning to breed.

-        MONTAGNE D'AMBRE:

Observations made from October to November. Most of the forest birds were breeding during this period.

-        SAMBIRANO:

Observations made from November to January. Many of the birds, both woodland and open-ground forms, were breeding or had just bred.

-        NORTHERN SAVANNA:

Observations made from September and November. Many birds were breeding.

-        WESTERN SAVANNA:

Observations made June to August, and February to April. In June, July, and August, from Tsiroanamandidy to Tsiandro, a few water birds were breeding. In February, March, and April, from Namoroka to Majunga, a few birds were breeding, many birds had young out of the nest, and apparently March and April marked the end of the breeding season for most of the birds.

-        SUBDESERT:

Observations made October to March. In October, November, and December many birds were breeding; in January a few birds were nesting (we did little field work during January); in February and March the breeding season was recently passed and many flocks of fledgling young were flying about.

The breeding season is correlated more or less with the rainy season, though on the east coast it starts before the rains. The breeding season in the Western Savanna is more prolonged than in the Subdesert where the rainfall is scanty. The woodland and forest birds are more restricted to a definite breeding season than are the water birds and the birds of the open ground, which may be found breeding throughout the year.

The dry season that is from May to October is the austral winter and during this season all breeding activities are at their lowest ebb.

In the Occidental and Subdesert many of the plants cease their activities.

Insects which probably would furnish food for the young of many species, even of seed-eating birds, are scarce. With the coming of the rains which, in the Occidental and Subdesert especially, herald the approach of another season of growth, plants send forth their leaves, insect life probably becomes more abundant, and perhaps because of this increased food supply for the young, many birds breed. In the Subdesert, where the rainy season is shortest, the breeding season is shortest. In the Occidental, with its longer rainy season and the probable occurrence of more abundant insect life over a longer period, the breeding season extends over a longer period. The birds of the Humid East that enjoy a damp climate the year around also breed during the summer (November to April). Some species seem to be restricted much less than others to a definite breeding season, though local conditions may in part account for this. The probable periodic activity of insect life is perhaps the obvious explanation for the restriction of the breeding season of many of these species. Further investigation will be required to test the truth of this theory. Other factors, among them the time of ripening of fruits and seeds, may affect other species; and only knowledge of the life history and ecology of each species will enable one to understand its time of breeding.