Researchers Study Causes of Chick Mortality
Victoria Dreitz, Colorado Division of Wildlife |
The mountain plover is a migratory upland shorebird, and it's a species of concern throughout its range due to suggested declines in population numbers. In Colorado, it’s believed that more than 50% of the continental population breeds across the eastern plains, with smaller breeding populations in arid areas in western parts of the state as well as the high elevation valleys, such as South Park and the San Luis Valley.
On the eastern plains of Colorado, mountain plovers breed primarily on shortgrass prairie habitats, which consist of rangelands with and without black-tailed prairie dogs and dryland agricultural fields. The Colorado Division of Wildlife supports research to understand if and how the use of different breeding habitats in eastern Colorado play a role in the suggested declines of the continental population.
A study conducted from 2001 to 2003- with cooperation from the U.S. Fish and Wildlife Service, U.S. Geological Survey, Colorado Farm Bureau, the Colorado Natural Heritage Program and other agencies- suggested that nest survival rates are similar among the breeding habitats used by mountain plovers in eastern Colorado. A more recent study conducted by CDOW suggests that chick survival and brood movement patterns differ between various habitats and were unrelated to differences in prey (insect) availability. Check out the Mountain Plover Research page for more information about ongoing research.
Different causes of chick mortality may account for the variations in survival rates among different habitats. To determine the cause of chick mortality, individual chicks need to be monitored regularly from the hatching through fledgling stages. Radio telemetry is the most feasible way to do this.
The CDOW uses radio telemetry to gather information on species such as deer, elk, and lynx. Only within the last few years have miniature-sized radio transmitters (≤ 0.35 grams) been developed. This transmitter is small enough to use on a 10 gram newly hatched mountain plover chick.
From 2007-2009, the CDOW tested the potential impact of placing radio transmitters on small growing mountain plover chicks. This involved captive work on surrogate species and field testing to determine the following:
the best method to attach transmitters to chicks;
- distance range in which chicks with transmitters can be located;
- possibility of finding buried transmitters or those taken into burrows;
- ability and distance to locate transmitters by aircraft;
- how often do chicks need to be monitored to determine the cause of mortality;
- and how frequently can the cause of mortality be distinguished as either predation, weather conditions, starvation or another cause.
The CDOW will start collecting field data in mid-April through late-August of 2010 in which we will monitor mountain plover chicks with radio transmitters. If a chick dies, it will be assessed whether the cause of mortality was predation, weather conditions, starvation, or another cause. This research study will be conducted in collaboration with numerous private landowners who've allowed access to their lands in Lincoln and Kiowa counties.
Similar research studies are being conducted simultaneously at other breeding sites outside of Colorado as part of a range-wide assessment on mountain plover chick ecology. The CDOW is collaborating with U.S. Fish and Wildlife Service, Iowa State University and Colorado State University in this range-wide assessment.