Occupancy and Richness of Colorado Breeding Grassland Birds: Estimation
Investigator: Paul Doherty
Graduate Student: Heather Tipton
Project Start Date: 08/04
Expected Completion Date: 12/06
Funding Agency: Colorado Division of Wildlife
Over the last 40 years, shortgrass prairie birds have shown consistent,
widespread declines. These declines may be a result of anthropogenic
changes to the prairie landscape such as land conversion/cultivation,
alteration of native grazing assemblages and regimes, and fire
suppression. As wildlife biologists have attempted to address
these declines and
better manage avian species of concern, they have focused on
developing monitoring schemes and identifying avian-habitat associations.
One potentially important habitat relationship is with one of
remaining native grazers, the black-tailed prairie dog (Cynomys
ludovicianus). Studies have suggested that prairie dog colonies have
densities and are more species rich than uncolonized areas. However,
methodologies widely used to estimate grassland bird population
parameters to date have lacked at least one of two important considerations,
namely attention to a probability-based sampling scheme and incorporation
of detection probability into estimates of abundance/density. This
project focuses on these methodology issues as well as habitat
The information obtained will be useful in advancing monitoring
methods for shortgrass prairie bird communities and in directing
management and acquisition/conservation efforts.
Estimation methods will be evaluated and applied to grassland
bird populations in Colorado’s shortgrass prairie.
1) Evaluate occupancy and double observer methodologies (which
incorporate detection error) to estimate density, occupancy
and richness using a
probability-based sampling scheme.
2) Apply these methods to examine and compare the density,
presence, and richness of avian species across three strata
colonies, uncolonized grassland, and dryland agriculture) in
prairie ecosystem of eastern Colorado. In doing so, we will
test the prediction
that prairie dog colonies have higher densities, higher occupancy
probabilities, and greater richness of grassland birds than
other habitat types.
Progress: To date Heather Tipton has conducted a pilot study
and is in the process of writing her proposal. Heather is continuing
and will begin her first formal field season this spring. During
the week of March 7th, Heather defended her thesis proposal.