Saturday, June 2, 2018

Surveying birds in the national parks of the west

Posted by Amanda Gallinat

“It is in vain to dream of a wildness distant from ourselves. There is none such.”
-Thoreau in his Journal, 30 August 1856

This spring, my partner Sam Roberts and I are surveying birds for the National Park Service out west. Between early-May and early-July we will have surveyed twelve parks across the Northern Colorado Plateau Network (NCPN), which is a region of parks located primarily in Utah and Colorado. Launched in 2005, the goal of these annual bird surveys is to determine what bird species are using the parks in this region, how species densities are changing over time, and what is driving those changes.

Sam uses a rangefinder to measure the distance to a Juniper Titmouse in pinyon-juniper habitat at Capitol Reef National Park

To determine which birds are present and in what densities, we use a point count method. Every day before sunrise, Sam and I each navigate to a transect located in one of three target habitats: riparian, pinyon-juniper, or sage. At each of fifteen points along the transect, we then look and listen for any and all birds for five minutes, recording the species of each bird and the distance it is from us. For the most part, we detect small songbirds that are breeding in the area.

We identify most birds by their songs and calls; in this video, taken in sage habitat at Bryce Canyon National Park, you can hear a nearby Western Meadowlark

Sampling with point counts allows us to estimate changes in the densities of birds over the past thirteen years of the project. Birds with densities that have declined significantly over that time include Black-throated Gray Warblers (primarily associated with pinyon-juniper habitat), Lazuli Buntings (riparian habitat), and Sage Sparrows (sage habitat).

Lazuli Buntings breed in riparian habitat, and are declining in density in the NCPN; Photo by Alix d'Entremont via the Macaulay Library

We also conduct habitat/vegetation surveys at each point, recording information like the height, abundance, and plant species present in the canopy, shrub, and ground cover, as well as the presence of snags, tamarisk, bare rocks/cliffs, and prairie dog towns.

Me, noting the presence of (lots of!) tamarisk during a vegetation survey in a riparian transect

One next step for this project, in addition to continuing long-term monitoring, is to identify the drivers of changing bird densities. Possible predictors include the habitat/vegetation characteristics we have been recording, as well as remotely sensed information like precipitation patterns. You can find more information on this project, run by the NCPN and the Shriver Lab at the University of Delaware, here. Read last year’s annual report here.

No comments:

Post a Comment