Spotting Songbirds in the Rockies
Worldwide many species of birds have experienced pronounced population declines over the past 30 years. Nationally and internationally, understanding bird populations within human-dominated landscapes is crucial to enable us to ensure important breeding habitats are not lost. Declining population trends must be identified and reversed locally to create positive change globally.With the help of Earthwatch volunteers, Dr. Embere Hall and her team are trying to do just this, and have made links between levels of human development and the decline of songbird populations in the United States. Grand Teton National Park and Bridger-Teton National Forest (both parts of the Greater Yellowstone Ecosystem) near Jackson Hole, Wyoming, have been at the centre of the research.
This picturesque area is surrounded by a stunning backdrop of mountains and valleys and is home to abundant wildlife such as bison, wolves, bears and, of course, a vast array of songbird species. The partnership between Dr. Hall and Earthwatch goes back to 2008 (although songbirds in the area have been studied for the past 16 years by the Conservation Research Centre of the Teton Science Schools in Jackson Hole, Wyoming), bringing volunteers into the field to assist the team with attempting to identify why resident and migratory songbird species have been declining.
Bander Chris Hansen clamps a tiny band on a flycatcher.
Birds are excellent ecological indicators, with their presence or absence giving insights into habitat quality, making this project vitally important in advising the protection and conservation of sensitive and valuable habitats. The monitoring and research data provide important baseline information on the condition of the riverside habitat.
Mist netting and leg banding
During the 2010 field season, mist-nets were deployed at five sites to capture birds, enabling the scientists to measure levels of recapture (birds that have been caught previously and tagged with a unique colour band), and therefore estimate levels of survivorship and productivity rates. This is part of the Monitoring Avian Productivity and Survivorship (MAPS) program to influence policy and management. 1,562 birds were captured from 58 different species, 32% of which were recaptures. The most commonly captured birds included yellow warbler (Dendroica petechia; 360), western tanager (Piranga ludoviciana; 126), American robin (Turdus migratorius; 106), song sparrow (Melospiza melodia; 72), and cedar waxwing (Bombycilla cedrorum; 64).
Reproduction levels were estimated by working out the ratio between birds born that year (hatch-year) and birds born before that year (after hatch-year), identified by examining plumage. Although the mist-netting data from 1998 to 2010 did not show a strong relationship between productivity of the birds and the levels of housing development, the volunteer data has helped the team to better understand how much variability exists in the reproductive productivity of the birds, both within and between the seasons.
To further estimate levels of annual adult probability for survival, the volunteers noted sightings of previously banded birds from three riparian (riverside) species: black-headed grosbeak (Pheucticus melanocephalus; 4 resighted), song sparrow (14 resighted) and yellow warbler (38 resighted). Combining this resighting data with the data from mist-netting has enabled the scientists to produce viable survivorship estimates which they can now use to model bird populations at different intensities of human development.
Project staff and Earthwatch volunteers identified 107 active nest sites of four species in 2010. The sites covered areas of varying urban development, so that comparisons could be made between areas of high and low development. Analysis of data from 2008 to 2010 indicated that human development may reduce nest survival, though the reasons for this are still not clear. The trend is not clear because in the past two years less developed sites showed higher success rates, but in 2010 less developed sites showed lower nest survival compared to more developed sites. This departure from the previous two years alongside information on nest success patterns may be due to the cooler and wetter weather that was observed at the start of the nesting season. The overall indication is that while songbirds breed in sites surrounded by development, the likelihood of fledging young is reduced relative to sites in less disturbed landscapes. During the winter of 2010/11, a more advanced nest survival model was implemented to further investigate this, taking into account time of year and season.
The research area is surrounded by a stunning backdrop of mountains and valleys.
Another of the research objectives of this project is to encourage local communities to take responsibility for their environment and encourage effective management of natural resources among local groups and policy makers. The partnerships that this project has formed are of paramount importance to its success. They include The Raynes Wildlife Fund, a citizen-science organization which shares the data collected by Earthwatch teams with a wider audience through its website, informing and engaging local people, including children, in the conservation of their local environment and the songbird species. During the summer of 2010 collaboration with Nature Mapping Jackson Hole - a local citizen science group dedicated to 'keeping common wildlife common' - was enhanced through the training of 24 project volunteers in bird identification, colour-band reading and basic ornithology.
New for 2011
In 2010 quantification of nest predators at each research site was carried out for the first time by documenting relative abundance of corvid species - the Corvidae being the family of birds that includes jays, crows, ravens and magpies. Preliminary analyses of songbird nest survival indicates that variation in the predator community may be another explanation behind the trend of lower nest success in developed landscapes, giving us insight into the cascading effects that human development can have on natural systems. Research has shown that the behaviour and population demographics of various corvid species (specifically crows, ravens, and jays) can correlate with proximity to human development, to varying degrees depending on species. This shall be investigated further in 2011 to identify long-term patterns.
Volunteers enjoying the birdwatching on the project.
Work for the future
While patterns and trends are starting to be drawn out from the research on songbirds in the Grand Teton National Park, such as the indication of a decline in success of the population closer to urban environments, more data is needed to analyse patterns in the long term. To halt the decline of songbird species that has occurred in the area for 30 years, it is imperative that population dynamics and levels of survivorship relative to human developments are fully explored and understood, in order to provide comprehensive protection for species and their habitats to retain viable populations.
Get involved: find out more about joining Spotting Songbirds in the Rockies as a volunteer.
Report by Sophie Thompson.