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Cycle 2 (2012 Deadline)
Climate change and arid-zone birds: validation of a behavioral index for assessing species’ relative vulnerabilities to rising temperatures
PI: Andrew McKechnie (University of Pretoria)
U.S. Partner: Blair Wolf (University of New Mexico)
Project Dates: August 2013 to March 2016
|An aviary under assembly at Murray Game Ranch, an 11,000–hectare property outside the town of Askham in the Northern Cape province of South Africa. Photo courtesy: Dr. McKechnie.|
Predicting the impacts of climate change on birds is one of the greatest challenges currently facing ornithologists. A priori, bird communities inhabiting hot desert environments may be expected to be among the vulnerable to rising temperatures, on account of the thermal stresses and unpredictable water and food resources encountered in these habitats. Increasing temperatures in hot deserts are predicted to cause bird range changes, but at present we have no capacity to predict which species will respond first or when the response will occur. Making such predictions requires a mechanistic understanding of the links between the physical/environmental characteristics of habitats and organismal performance. The physiological research needed to elucidate these links requires time-consuming and intensive study of individual species, making this approach generally unsuitable for anything more than a small subset of the species that make up arid-zone bird communities. The research to be carried out as part of this PEER Science project seeks to validate a behavioral index of vulnerability to heat stress in birds inhabiting hot desert environments. Dr. McKechnie and his team will test predictions that relate heat dissipation behaviors to underlying changes in body temperature and hydration status in model species that vary in terms of the relationship between environmental temperature and heat dissipation behaviors. The over-arching aim of this research is essentially to develop a rapid assessment tool, whereby the relative vulnerabilities of birds making up arid-zone communities to more frequent and severe heat waves can be assessed largely on the basis of behavioral observations. The development of such a rapid assessment tool will mean that the species most vulnerable to the impacts of climate change can be identified in any desert environment, anywhere in the world, on the basis of readily collectable behavioral data.
This project is directly relevant to USAID’s Environment and Global Climate Change focus area. It relates to aspects of the Global Climate Change component (helping conservationists and other environmental stake-holders “prepare for and respond to changes in climate”) as well as the Conserving Biodiversity component. Birds provide a host of vital ecosystem services, including pollination, seed dispersal, and insect pest control, and the identification of those avian taxa most vulnerable to rising temperatures has far-reaching implications for predicting how climate change will affect arid-zone ecosystems and the human communities that depend on them. This project is focused on a global scale, and although the researchers will work in one specific desert (the Kalahari of southern Africa), the outcomes of this research will be applicable globally. This project will also provide opportunities to train several students, with an emphasis on recruiting students from historically disadvantaged sectors of the South African population. Moreover, this research will strengthen links between South African institutions and their U.S. counterparts and will pave the way for future collaborative research in related fields. Even though this study will focus on birds inhabiting desert habitats, the researchers are using desert systems as a “proving ground” for a conceptual framework that should be able to predict climate change impacts among birds inhabiting other biomes, including tropical forests.
Summary of Recent Activities
The reporting period saw the second half of the summer 2014/15 field season, with Michelle Thompson (PhD student) based at the field site near Askham, Northern Cape Province, South Africa until mid-March. During this time, she completed data collection for aviary populations of four of our study species, namely Laughing Dove, Namaqua Dove, Cape Glossy Starling, and White-browed Sparrow-weaver. This brings the total number of species for which the team has aviary data to seven (the previously mentioned four plus Fawn-colored Lark, Sociable Weaver and Red-eyed Bulbul examined during the first field season (summer 2013/14). The difference between this number and the nine or ten species specified in the original project plan reflects the difficulties the team has encountered with temperature logger failure, and the fact that Michelle hence had to repeat data collection for several species she worked on during the first half of the season.
The data collected during the reporting period can be summarized as follows:
- Behavioral data (presence/absence of heat dissipation behavior) necessary to calculate HD50 values in captivity for White-browed Sparrow-weavers, plus additional data for Laughing Dove, Namaqua Dove and Cape Glossy Starling.
- Body temperature data – core body temperature over six weeks, including water restriction experiments, using Holohil VHF transmitters for Laughing Dove, Namaqua Dove, Cape Glossy Starling (additional data collection because of the equipment failures experienced during the first half of the field season), and White-browed Sparrow-weaver (new study species for which no data had been collected).
- Blood samples necessary for estimating total body water via isotope dilution for White-browed Sparrow-weavers, plus additional data for Laughing Dove, Namaqua Dove and Cape Glossy Starling.
In July, the team will present its results at a local conference (Zoological Society of Southern Africa annual meeting). The team will also analyze and start writing manuscripts based on the body temperature data collected so far. Most of the manuscripts that will emanate from this study will be based on data for all the study species (so will only be finalized after the third and final field season). Nevertheless, one manuscript on patterns of body temperature among the seven species for which there is data will be prepared and submitted for publication by the end of 2015. Moreover, Susie Cunningham (co-supervisor of Michelle Thompson) is currently working on a manuscript based on the unexpected finding that, among the study species examined to date, dominance status of individual birds is correlated with mean daytime body temperature. This finding is peripheral to the key questions driving this project, but nevertheless has considerable scientific novelty and will provide an additional output from the project. The research team anticipates submitting a manuscript to the journal Biology Letters in the 3rd quarter of 2015. The team will also begin preparations for third and final field season. Michelle Thompson will spend several months in the field next summer collecting data for a further 2-3 species in order to bring the total up to the 9-10 specified in the original project plan.
|Michelle and Nicholas discovering various Arizona desert species during their behavioral data collection fieldwork in Arizona, July 2014. Photo courtesy: Dr. McKechnie.|
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