Understanding urban raptor populations | FitzPatrick Institute of African Ornithology

Urban development is increasing across the globe and poses a major threat to biodiversity, which is often relatively low in human-modified landscapes. After climate change, the United Nations considers urbanisation to be the biggest environmental challenge to the maintenance of biodiversity. Globally, there are now more people living in urban than in rural areas, and the trend towards urbanisation is faster in Africa and Asia than in any other regions of the world.

The Cape Peninsula is located on the southern tip of the African continent, where climate change is predicted to be particularly rapid and severe. In this project we focus on the responses of raptors to increasing urbanisation under climate change. On the Cape Peninsula, urban breeding Peregrine Falcons Falco peregrinus and Black Sparrow-hawks Accipiter melanoleucus have been monitored for over 30 and 20 years, respectively. During this time, the populations of both species have increased markedly within the study area. Both species profit from the abundance of suitable nesting sites and their favoured avian prey, including pigeons, doves and Common Starlings Sturnus vulgaris. We use these two long-term data sets on individually-marked birds to investigate the effects of urban-living and weather on breeding phenology, reproductive performance and population trends.

Besides habitat loss and fragmentation, wildlife in urban areas might also be negatively affected by altered bio-geochemical cycles and the introduction of novel urban stressors such as light, sound and chemical pollutants. Urban-exploiting or adaptable species that are able to make use of abundant resources in the short-term, might thus still suffer from other hidden costs of urban living, which could undermine their long-term health and persistence in urban environments. We use the Black Sparrowhawk study system and a biomarker approach to investigate such possible health impacts. Taking small blood samples from adults and their offspring, we have quantified eco-physiological parameters such as immune assays, oxidative stress and dietary antioxidants. The eco-physiological component of this research has been carried out in collaboration with Lund University, Sweden, as part of a bilateral project funded by the NRF and STINT which ended in 2020.

Activities in 2020

Although the COVID-19 pandemic made field work difficult, we ringed 30 Black Sparrowhawk nestlings from 15 territories in 2020.
Together with Assoc. Prof. Caroline Isaksson from Lund University, we finalised the three-year joint NRF/STINT South Africa-Sweden research collaboration focusing on urban avian ecology. We continued writing a review paper and several original research papers. Arjun Amar and Caroline Isaksson presented a summary of the completed project at the NRF/STINT closing ceremony.

Highlights

A paper on the influences of weather and urbanisation on Peregrine Falcon phenology and breeding success was published by Petra Sumasgutner, Andrew Jenkins, Arjun Amar and Res Altwegg in PLoS One. The paper used Andrew’s long-term dataset on breeding peregrines in Cape Town and highlighted the value of nest boxes for the species in a changing environment.
Rebecca Muller published a paper in Condor - Ornithological Applications. Data collection was undertaken in collaboration with Dr Shane McPherson and Prof. Colleen Downs (UKZN) and unravelled the productivity of urban Crowned Eagles Stephanoaetus coronatus.
Drs Petra Sumasgutner and Shane McPherson gave an invited talk at the 7^th North American Ornithological Conference (NAOC) in a Round Table Discussion about the use of drones in avian research, specifically to survey raptor and raven nests in anthropogenic landscapes.
Drs Chevonne Reynolds and Petra Sumasgutner wrote a chapter on urban animal diversity in the Springer Book Urban Ecology in the Global South (currently in press) which specifically highlights the role of predators for functional diversity in cities.

Impact of the project

The project is one of the first to examine individual health and productivity of a bird species in relation to urbanisation in Africa. Our results have considerable implications for potential changes in phenology or productivity for the regions’ avifauna as African urbanisation continues.

Key co-supporters

DSI-NRF CoE grant; NRF-STINT South Africa-Sweden Research Collaboration, Claude Leon Foundation.

Research team 2020

A/Prof. Arjun Amar (FIAO, UCT)
Dr Chima Nwaogu (FIAO, UCT)
Prof. Res Altwegg (SEEC, UCT)
Dr Andrew Jenkins (ADU, UCT)
Dr Petra Sumasgutner (FIAO, UCT & U. Vienna)
Dr Arne Hegemann (MEEL, Lund University)
A/Prof. Caroline Isaksson (MEEL, Lund University)
Dr Hannah Watson (MEEL, Lund University)
Prof. Colleen Downs (UKZN)
Dr Shane McPherson (UKZN)

Student: Carina Nebel (PhD, UCT).

Research Assistants: Rebecca Muller, Burghen Siebert.

Volunteers: Ann Koeslag, Marlene Hofmeyr, Paddy Walker, Margaret MacIver, Antje and Bernard Madden.

Two curious Black Sparrowhawk nestlings peek over the rim of their nest. Both chicks were ringed as part of the long-term monitoring of the Black Sparrowhawks in Cape Town (Photo: Marlene Hofmeyr)

A Black Sparrowhawk nestling that was ringed by our project is fed by its mother. The ringing of Black Sparrowhawk nestlings is a vital effort in obtaining long-term data on the species (Photo: Marlene Hofmeyr).

A pair of mating Black Sparrowhawks. We found evidence of ageing in the reproductive performance of Black Sparrowhawks, but ageing did not differ across an urbanisation gradient (Photo: Colin Brown).

A light morph Black Sparrowhawk perches on a pine tree at the foot of Lion's Head. This species is very successful in urban habitats with some pairs breeding in suburban backyards (Photo: Paddy Walker).

We assessed how diet differences between urban and ‘rural’ Peregrine Falcons might influence their demography, based on Andrew Jenkin’s 30-year study of the Cape Town population (Photo: Andrew Jenkins).

A colour-ringed Peregrine Falcon in Mitchell's Plain. Andrew Jenkins has been monitoring the population on the Cape Peninsula for the last 30 years (Photo: Andrew Jenkins).

Carina Nebel and Petra Sumasgutner inspecting stress bars in the growing feathers of a Black Sparrowhawk chick. Fellow students and raptor enthusiasts are invited to join the ringing events, here Gabriella Leighton is photographing the process. (Photo: Sanjo Rose).

A resighting of a Black Sparrowhawk male, ringed in 2011, on a Speckled Pigeon Columba guinea in Silvermine Village, near Noordhoek (Photo: Dave Black)

Black Sparrowhawk nestlings, approximately 5 and 11 days old, photographed while a nest camera was being installed. The disturbance to the nest was less than 20 minutes and the female returned immediately after we left the site to brood her offspring (Photo: Shane McPherson)

A female Black Sparrowhawk, with her chick on the nest (Photo: Ann Koeslag)

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