<b>Highly variable breeding phenology in an arid region colonial cooperative breeder, the Sociable Weaver</b>

Code and data for: <b>Highly variable breeding phenology in an arid region colonial cooperative breeder, the Sociable Weaver</b><br>Describing breeding phenology – the timings of reproductive events – is central for studying individual fitness and population dynamics. While fundamental differences in breeding strategies between different biomes (e.g. tropics and temperate regions) have long been identified, detailed descriptions based on long-term studies of individually marked birds are biased towards North American and European bird populations. As a result, crucial information on bird breeding phenology remains scarce in bird diversity hotspots such as southern Africa, an area that is also highly threatened by climate change. In most of the Southern hemisphere arid regions, especially in southern Africa and Australia, rainfall patterns are often erratic, leading to variation in the duration of the conditions suitable for breeding within and between years. These dynamic environmental conditions select for flexible and opportunistic breeding strategies. Consequently, breeding seasons vary from year to year both in length and intensity – from skipping breeding to prolonged breeding with multiple attempts per couple. Here, we report on the highly variable breeding cycle of the Sociable Weaver Philetairus socius, a colonial cooperatively breeding passerine from the arid savannahs of the Kalahari region of southern Africa. We monitored the reproduction of an individually marked population over 11 years. Breeding activity usually started at the end of winter, but varied greatly in starting date as well as duration (from 4 to 11 months). The percentage of active nests also changed greatly within and between seasons. As a result, the yearly number of clutches per female changed markedly between years, leading to extreme cases such as a female that laid 8 clutches in a year (and others suspected to lay up to 13), which is one of the highest numbers reported for any wild bird species.