A project of


Mountain Birdwatch uses rigorously tested methods developed by statisticians and biologists and implemented by a cadre of field-savvy citizen-scientists.

Mountain Birdwatch Past and Present


Initiated by the Vermont Center for Ecostudies in 2000, Mountain Birdwatch has always relied on citizen-scientists to conduct annual counts along survey routes throughout the mountains of New England and New York. Originally, Mountain Birdwatch focused on five species: Bicknell’s Thrush, Swainson’s Thrush, Blackpoll Warbler, White-throated Sparrow, and Winter Wren. Between 2001 and 2010, observers annually surveyed more than 100 routes in New York, Vermont, New Hampshire, and Maine.


In 2010, we launched an improved version of Mountain Birdwatch, which included a new, statistically based selection of routes across the northeastern United States and a revised survey protocol to allow for more stringent and intensive statistical analyses (for an example from recent research, read this paper). With our colleagues at Bird Studies Canada and the Canadian Wildlife Service, we also expanded Mountain Birdwatch to include the highlands and mountains of Quebec, New Brunswick, and Nova Scotia. Mountain Birdwatch now consists of 759 survey points located on 137 routes across four states and three provinces. Each point is surveyed annually by one of the more than 100 citizen-scientists now participating in Mountain Birdwatch.

The new version of Mountain Birdwatch also expanded the number of species included, allowing us to track populations of Yellow-bellied Flycatcher, Boreal Chickadee, Black-capped Chickadee, Hermit Thrush, and Fox Sparrow, in addition to the original group of Mountain Birdwatch species.

Counting Birds

We designed the Mountain Birdwatch surveys to acheive three main goals:

  1. To estimate on an annual basis the abundance of target species.
  2. To measure changes in the abundance of target species over time.
  3. To relate trends in abundance to biotic and abiotic variables that may
    affect the target species.

Bird Survey Methods

The Mountain Birdwatch protocol consists of four consecutive 5-minute counts at each survey station, for a total sampling period of 20 minutes per point. Observers conduct repeated counts for all target species during each 5-minute period, noting whether individuals were detected within 50 meters of the point. During the first 10 minutes of the survey, observers track individual Bicknell’s Thrushes within four distance categories (<25 meters from the point, >25 – 50 meters, >50 – 100 meters, and beyond 100 meters) on a minute-by-minute basis.

Surveys are conducted during the month of June, which is the period of greatest singing activity for the target species. In order to increase the likelihood of detecting Bicknell’s Thrush, which is most vocal during the pre-dawn period, observers begin surveys 45 minutes before sunrise.

Inclement weather can greatly reduce an observer’s ability to detect birds in the field, so each survey is conducted when temperatures are above 35ºF and when precipitation and wind conditions are favorable. Occasional drizzle or a brief shower is acceptable, but surveys are not conducted during periods of steady drizzle or prolonged rain. Likewise, a light wind with occasional gusts is considered acceptable weather for surveying birds, but a stiff breeze of >18 miles per hour is not.

Analyzing Data

VCE scientists have used the most current and cutting-edge methods to analyze the data collected by Mountain Birdwatch’s citizen-scientists. By taking advantage of sophisticated statistical models, scientists can transform the simple counts into estimates of density – the number of individuals per unit area – while accounting for the reality that not all individual birds present during a survey will be detected by the observer. The statistical models can also account for variation in observer acuity (for example, some of us can hear the faint trill of a Blackpoll Warbler better than others!), variation in weather conditions that affect the behavior of birds, and seasonal and daily changes in the frequency of singing. For example, an observer may be more likely to detect Bicknell’s Thrush at a survey conducted early in the morning or during a survey conducted earlier in the month of June; our statistical models can account for these hidden sources of variation.

A recent paper published by Jason Hill and John Lloyd provides a good example of how Mountain Birdwatch data can be used to inform our understanding of our mountain birds. In this paper, they analyzed Mountain Birdwatch data collected from 2011-2016 to estimate the population size of Bicknell’s Thrush in the US (as of 2016, they estimated that between 56,080 and 89,748 Bicknell’s Thrush were present in the US). They also used statistical models to predict the abundance of Bicknell’s Thrush in approximately 1-hectare blocks throughout the US, yielding the first-ever fine-scale abundance map of Bicknell’s Thrush. With the creation of this map, the number of Bicknell’s Thrush likely present at any particular location within their US range can be predicted! You can try this out for yourself using the dynamic mapping tool at DataBasin.

This analysis has many potential applications for conservation; for example, allowing decision-makers to evaluate the likely affects on Bicknell’s Thrush of development in the high country. The analysis also identified gaps in the protection of Bicknell’s Thrush, noting that roughly 15% of the population occurred on unprotected lands. Most of this unprotected land was found in the commercial forests of western Maine, highlighting the importance of working with forestry companies to implement sensible conservation measures. Overall, the results reinforce the importance of taking positive action to conserve habitat for Bicknell’s Thrush. By combining their results with existing estimates of population size in Canada, Hill and Lloyd figured that the total number of Bicknell’s Thrush in the world was less than 120,000, meaning that Bicknell’s Thrush has one of the smallest population sizes of any regularly occurring bird species within the contiguous U.S. and Canada.

It is important to note that none of this information would have been uncovered were it not for the hard work of the citizen-scientists that carry out Mountain Birdwatch. Especially valuable were the consistent efforts of citizen-scientists who have adopted routes that rarely support Bicknell’s Thrush – knowing where they are not is just as important as knowing where they are!

Want more information about the numbers in this report? See Making Sense of the Numbers.

Interested in reading more about how these data are used to help protect species and their habitat? Read about how we translate science into action.

State of Mountain Birds