Bird community seasonality and long‐term changes in migrant birds across a large savanna protected area in South Africa

Migratory bird species fascinate humanity but also contribute significantly to the ecosystems they visit in various ways (e.g. food web structures) and can thus be considered good environmental indicators. Although protected areas (PAs) should play an important role in the conservation of migratory species, this is not always achieved; for example, South Africa (of which the world‐renowned Kruger National Park is among the top five largest PAs across southern African countries) meets the minimum threshold of 17% PA coverage by 2020 for global migratory species, as set out by the Strategic Plan for Biodiversity 2011–2020, Target 11. Nonetheless, little is known about how bird communities and migratory functional groups across the park respond to seasonal variation and whether their phenology and abundances have shifted over time. We investigated whether bird diversity differed among seasons and whether intra‐African and Palearctic migratory bird community arrival and departure times, as well as abundances, changed over a 30‐year period in a large protected area, the Kruger National Park, South Africa. We used bird species occurrence data and subsequent reporting rates (a proxy of abundance) from the first and second Southern African Bird Atlas Projects (SABAP1 and SABAP2). We computed three diversity indices and used a non‐linear least squares modelling approach. Unsurprisingly, we found that species richness was significantly lower when the migrant birds were absent during the Austral winter; however, functional and phylogenetic diversity remained unchanged. We also found that no shifts in the arrival or departure months occurred over the last 30 years, but, more concerning, the abundances of specifically the intra‐African migrant populations were reduced by 20% overall, including abundant species such as Senegal Lapwing Vanellus lugubris for which a > 60% decrease in reporting rate occurred. The causes of these declines, however, remain uncertain because we have not tested for the effects of any (e.g. the El Niño‐Southern Oscillation), although unknown local (e.g. land cover change because of African Elephant Loxodonta africana impacts) and extra‐limital effects (e.g. anthropogenic habitat transformation) may have driven declines in the park. Our results show that identifying community‐wide declines in migrant bird functional groups can be a starting point towards more focused, single‐species conservation action that PA management and non‐government organizations should support.