When the Ruby-crowned Kinglet sings at dawn, observers may detect the loud and clear notes of the intrepid songbird. No change was detected in abundance for the remaining species of songbirds. Thus, in 2009, Fox Sparrow abundance was 250 percent (2.5 times) greater while WilsonвЂ™s Warbler abundance was 50 percent (half) what it had been in 1995. Over the 15-year study period, they estimated that on average along the park road, Fox Sparrow abundance increased at a rate of 6.4 percent per year while WilsonвЂ™s Warbler abundance decreased at a rate of 4.3 percent per year. This вЂњobserver effectвЂќ must be incorporated into calculations of abundance and estimates of trends.ДЄfter accounting for these three sources of variation in detection, researchers can estimate trends with confidence. The field crew returns to sampling points several times (3-12 for roadside, 2-3 for off-road) during the season.Дifferences in detection of three bird species by three observersДЄlthough all Denali observers are trained intensively and are proficient at identifying birds in the study area, there are very large differences in detections of songbirds among even highly-trained observers (see graph at left). Surveys start within ВЅ hour of sunrise and continue for about six hours.

The surveys start in late April when resident species are nesting and migratory species are setting up nesting territories and end in mid-July when males sing less. The observer also records environmental data including weather conditions and background noise. Statisticians also reviewed previously collected data from 1995 to 2009.ДЇor repeat bird surveys in Denali, observers conduct bird surveys at 150 points along the park road spaced 0.5 mile (800 m) apart and at more than 600 points located up to 7 miles (12 km) away from the park road spaced about 0.3 miles (500 m) apart.ДЄt each sampling point, an observer records all the birds detected during the timed survey (three minutes for roadside sites or ten minutes for off-road sites). To answer these questions, i.e., to determine whether the probability of detecting each species changes across the nesting season, during the sampling day, and with different observers, beginning in 2009, researchers and field assistants have conducted repeat-surveys during the nesting season for songbirds in Denali. To plan surveys that can be used reliably to compute population estimates for comparisons from year to year, researchers and statisticians with the passerine monitoring program for Denali and the other two parks in the Central Alaska Network (CAKN) asked three questions: Does it matter when during the nesting season surveys are conducted? Do bird species have different singing habits, so that the time of day would influence the survey results? Are the results consistent from one observer to another? Since 2002, the protocol for monitoring passerine birds has undergone extensive revisions to incorporate new survey and analysis methods. Population estimates depend on the survey technique used and must take into account the factors that influence bird detectability (ability to see the bird or hear a song). But the estimate of population size for Ruby-crowned Kinglets in the sampling area is not just the total number of Kinglet songs heard during the surveys.

Songbirds are more often heard than seen during surveys. To assess whether bird species are increasing or decreasing in abundance over the years, it is critical that estimates of bird populations be based on accurate interpretations of the bird survey results. The Importance of Detecting Birds Reliably Passerines are found in all habitats in Denali ranging from wetlands to high alpine meadows. Passerine species in Denali include long-distance migrants such as flycatchers and warblers, and resident birds, such as Boreal Chickadee and Canada Jay. Songbirds belong to the Order Passeriformes or passerines. The goal of these surveys and the songbird monitoring program is to estimate accurately changes in songbird species abundance and distribution. But, being able to hear (or see) the Kinglet and other songbirds on their nesting grounds is the heart of the songbird surveys that biologists conduct in Denali National Park and Preserve. It is hard to imagine how a tiny bird like the Ruby-crowned Kinglet-which weighs only as much as two or three pennies yet migrates thousands of miles to nest in Denali-can sing so loudly. A dark-eyed junco, puffed up to stay warm.

Songbird species