Use of road kills and roadside vegetation by Pied and Cape Crows in semi-arid South Africa

Dean, Wrj; Milton, Suzanne J.; Anderson, Laura N.

doi:10.2989/00306520609485516

Cited by 18 publications

(18 citation statements)

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“…In South Africa, pied crows may extensively predate tortoises (Fincham and Lambrechts ). Pied crows are an adaptive species that benefit from human activities and favor habitat near roads (Dean and Milton , Dean et al ) such as the speckled tortoise study site. We often counted groups of 1–8 pied crows during the 2012 survey (average 47% of the time during 37 9‐hour observation days; T. Stark and C. Laurijssens, Homopus Research Foundation, unpublished data; Loehr et al ), whereas pied crows were estimated to be present <5% of the time in 2000–2004.…”

Section: Discussionmentioning

confidence: 99%

Unexpected decline in a population of speckled tortoises

Loehr¹

2017

J Wildl Manag

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Long‐lived, iteroparous species exhibit various mechanisms to overcome temporary unfavorable conditions and promote adult survival and population persistence. Consequently, populations may appear relatively stable while subtle and slow‐progressing threats cause their decline. The speckled tortoise (Homopus signatus) is a long‐lived, iteroparous species in South Africa that is thought to be secure in areas that meet the species’ known requirements. To verify its stability, I monitored a dense speckled tortoise population, integrating 2 mark‐recapture studies (2000–2004 and 2012–2015) in long‐term joint live and dead encounters and POPAN population models. From 2000 to 2015, the study site remained fenced, ungrazed, and was not modified in any way, yet the size‐class frequency distribution, sex ratio, and abundance of speckled tortoises drastically changed. Population numbers decreased 66%, mainly because of the disappearance of juveniles and males. Modeling results identified a reduction in the number of entrants into the population (via births and immigration) as the likely cause of population changes, whereas apparent survival remained high. Observations, in part anecdotal, of increasing numbers of pied crows (Corvus albus) on the study site suggest that increased predation on speckled tortoise hatchlings contributed to the population decline. Examination of rainfall data for 1990–2015 did not reveal evidence of aridification in the study area, a documented cause of reduced reproduction in speckled tortoises. The results of this study caution against the assumption that areas in the range of the speckled tortoise that meet its known requirements can maintain healthy populations. © 2017 The Wildlife Society

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Section: Discussionmentioning

confidence: 99%

Unexpected decline in a population of speckled tortoises

Loehr¹

2017

J Wildl Manag

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“…In 83% of the cases, the killed vultures were intended for sale to local restaurant operators or kebab sellers for onwards sale of the cooked meat to the unsuspecting public compared to 17% intended for black magic. The highest number of killed Hooded Vultures reported per each of such incidents was 32 and the last reported case was in 2012 [24]. Indeed, many of the vulture killing incidents may have gone unnoticed.…”

Section: Killing Of Vultures For Human Consumptionmentioning

confidence: 99%

“…A strong competition could therefore have ensued between the growing numbers of vultures and crows for a number of resources. Nevertheless, compared to Hooded Vultures, Pied Crows are known to forage on a wider range of food items including seed and fruits and are known to outcompete many species of birds [24]. Annorbah and Holbech (2012) indicated that crows transported stolen foods to faraway distances contrary to the vultures' frequent attempts to consume food items in the immediate vicinity.…”

Section: Competition Between Pied Crows and Hooded Vulturesmentioning

confidence: 99%

Some Important Observations on the Populations of Hooded VulturesNecrosyrtes monachusin Urban Ghana

Gbogbo

Roberts

Awotwe-Pratt³

2016

International Journal of Zoology

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Despite major declines in the population of vultures around the world, noticeable increases were reported in the populations of Hooded Vultures Necrosyrtes monachus over the past decade in Accra-an important vulture habitat in Ghana. In recent times, however, there is a growing concern that the vulture numbers are decreasing even though scientific data to support this is nonexisting. As a vital zoogeographical and conservation tool, it is important to keep an up-to-date knowledge about urban bird populations amidst rapid urbanization and associated changes. Using a combination of field data, literature review, and stakeholder consultations, it was indicative that severe decline might have indeed occurred in the populations of Hooded Vultures in Accra. Evidence suggests the killing of vultures for consumption, traditional medicine, and black magic in an undercover trade with possible transboundary connections as important underlying factor. Additional factors suspected to underlie the declines include changes in management of urban facilities and destruction of roosting and nesting trees. The implications of interspecific competition with Pied Crows Corvus albus on Hooded Vultures however remain unclear. There is an urgent need for conservation campaign and education to save the Hooded Vulture in Ghana.

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“…Within South Africa, it appears to have undergone large population increases over recent decades (e.g. Pied crows can occur at high densities in association with human settlements (Mwinyi & Said, 2009) and may be attracted to roads to forage on road kill (Dean et al, 2006). As a result of its wide distribution and generalist nature, it may be better able to cope with a changing climate than more specialized species (Simmons et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Electric crows: powerlines, climate change and the emergence of a native invader

Cunningham

Madden

Barnard

et al. 2015

Diversity and Distributions

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Aim Climate change and other anthropogenic global change drivers act in complex, mutually exacerbating ways to alter the abundance and distribution of species. In South Africa, pied crows Corvus albus have increased in numbers and range in recent decades. Popular opinion links these changes to urbanisation and infrastructure development, but there has been no empirical test of this idea. We aimed to clarify the drivers of pied crow population changes in South Africa.Location South Africa.Methods We used publicly available long-term datasets, the Southern African Bird Atlas Project and University of Delaware Gridded Climate Database, and spatial data from government bodies, to assess relationships between pied crow population and range changes, land use, infrastructure, urbanisation and climate change.Results Pied crow numbers have increased significantly in the past three decades, but rate of increase varied geographically, with crows declining in the northeast and increasing in the south-west of South Africa. Pied crow population changes were strongly correlated with climate change. Crows have benefited most from climate warming in the shrubland biomes of south-western South Africa. Pied crows are tree nesters, and within these shrublands, there is a strong positive relationship between the rate of population increase and the density of powerline infrastructure, which may facilitate pied crows' increase by providing nesting sites.Main conclusions Pied crow numbers have increased in response to climate warming, with their spread facilitated by electrical infrastructure in south-western South Africa, providing a clear example of compound influence of multiple global change drivers promoting a significant change in species range and reporting rate. Pied crows are generalist predators and there is popular concern about their ecological impact in areas where increases have occurred. We highlight the importance of understanding the ecosystem-level implications of increased numbers of pied crows in South Africa's shrubland biomes.

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Use of road kills and roadside vegetation by Pied and Cape Crows in semi-arid South Africa

Cited by 18 publications

References 0 publications

Unexpected decline in a population of speckled tortoises

Unexpected decline in a population of speckled tortoises

Some Important Observations on the Populations of Hooded VulturesNecrosyrtes monachusin Urban Ghana

Electric crows: powerlines, climate change and the emergence of a native invader

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