About This Project

Ask the Scientists

What is the context of this research?

Nitrogen is a key nutrient, but also a potential pollutant that naturally cycles globally between soils, water and air. Large urban areas can disturb natural cycling processes—they may become islands with few inputs or abnormally high concentrations. Either will disrupt natural cycling based on plants and microbes.

This project will investigate the importance of American crow (Corvus brachyrhynchos) feeding and roosting behavior in moving nitrogen across the landscape from natural and human-created food sources (e.g. rural agriculture and landfills) to “hot spots” of deposited nitrogen under roosts in urban forests. The roosts and resulting “hot spots” are likely to play a key role in the nutrition of urban plants and in the microbial processes that underlie the “biogeochemical cycles” occurring in our urban areas. The study of nutrient cycles in cities is in its early stages, but understanding them is key to designing healthy, ecologically sustainable urban environments.

What is the significance of this project?

Global changes in biodiversity and in biogeochemical cycles are two great challenges to sustainability of life in the 21st century. Our study links these challenges by connecting the natural behavior of animals to the biogeochemistry of a complex, urban-impacted landscape. Upstate New York is a patchwork of growing small-medium cities, rural agriculture and regenerated forest.

The research is grounded in a unique collaboration between ecosystem ecologists, Ben Eisenkop and Dr. Weixing Zhu and animal ecologists Dr. Anne B. Clark and Dr. Kevin J. McGowan. Drs. McGowan and Clark direct a 25-year population study of banded crows in Ithaca NY while Ben Eisenkop and Dr. Zhu will conduct the ecosystem study of soil nitrogen below roosts.

Ben’s research so far has identified a set of winter roosts ranging from large and traditional (10-50 thousand birds and used yearly) to small and transitory (<1000 birds and shifting year to year). We have demonstrated and worked out the methods for sampling and analyzing nitrogen and N-processing in soils below roosts year round.

The data produced by our study will demonstrate what role migratory bird movements play in the nutrient cycling between these areas, generating important data for understanding human-nature interactions in medium sized cities. A study of an iconic, familiar bird and the local parks or forests will also provide unique opportunities for environmental education at all levels.

What are the goals of the project?

To identify communal roosts in Ithaca, we will capture and fit 15-20 crows with radio-transmitters in fall of 2014. An additional 10-15 (to a total of 30 crows) will be tagged in Jan 2015 while migrants are present. The goal is to sample the movements and roost use of local crows year around as well as the winter movements of migrant crows.

Crows are trapped either in a drop-in trap, or using our remotely-triggered net (Net-Launcher) to capture specific families on territory. Clark and collaborator McGowan have used both methods successfully over the past decade for various behavior studies.

Captured birds are banded and given uniquely lettered wing tags for distance recognition. For radio tracking, birds are fitted with transmitters (wt. 6-10 g or <3% of the crow’s weight per USGS Bird Banding Lab guidelines) secured with a hand-fitted, back-pack style harness. All banding and radio-tagging is done under USGS and New York State permits to K. J. McGowan and all crow handling and observations are covered by IACUC protocols to Clark and McGowan. Tracking is done from vehicles with rooftop antennae connected to scanning receivers capable of efficiently moving through the set of radio frequencies. Repeat follows of individuals will reveal how regularly roosts are occupied and serve to identify more roosts. The habitat characteristics of roost sites will be quantified and their geographic characteristics recorded.

We will select three winter super roost sites in the region, three medium-large roosts in Ithaca, and three reference sites with no known roost history. Roost deposition will be collected on site in winter (Dec-Feb) twice a month, and in spring (Mar-May), summer (Jun-Aug) and fall (Sep-Nov) once a month; 5 collection points will be selected randomly along a 100m transect in each site, for a total of 675 samples. When roosts are not present, soil samples will be taken to measure lasting effects. These samples will then be brought back to our lab and analyzed for nitrogen content. From this, we can calculate the nitrogen flux of the landscape.