Breeding Bird Atlas 2 Full Reading The Accounts
This Breeding Bird Atlas 2 contains a summary of the distribution of breeding birds in Massachusetts from 2007 to 2011, as well as a comparison of those results with the first Massachustts Breeding Bird Atlas, which was undertaken from 1974 to 1979. The species are ordered in the book using the Fifty-Third Supplement (2012) to the American Orntihologists' Union Checklist of North American Birds, 7thEdition (1998).
Each species account consists of several parts, as noted in the following.
Every account includes a map of the bird’s Atlas 1 distribution, a map of its Atlas 2 distribution, and a map showing the statewide changes between the Atlases. This comparison of “snapshots” in time is at the heart of what makes a Breeding Bird Atlas such a useful tool since it allows us to witness with striking clarity the changes in bird communities over the past 35 years. Future Atlases will, in turn, be informed by comparison with the results of today’s Atlas.
Current status and trend; conservation statement, protected status – Each species account begins with a short summary of the species’ current distribution status and apparent trend since Atlas 1. Status descriptors are based on the percent of surveyed blocks where the bird was found during Atlas 2. The standard status descriptors include the following.
- Very local (found in 2% or less of all surveyed blocks)
- Local (found in 2-20% of blocks)
- Somewhat local (found in 20-35% of blocks)
- Fairly widespread (found in 35-50% of blocks)
- Widespread (found in 50-65% of blocks)
- Very widespread (found in 65-80% of blocks)
- Nearly ubiquitous (found in 80% or more of blocks)
- Trend descriptors are based on the change in block occupancy between Atlas 1 and Atlas 2, and use the “change” data set. The metric is the percent of blocks occupied in Atlas 1 that are still occupied as of Atlas 2. If a species occupies the same number of blocks in Atlas 2 as it did in Atlas 1, then its metric is 100%. The standard trend descriptors include the following.
- Strongly increasing (>200% occupancy)
- Likely increasing (>110%-200% occupancy)
- Stable (>100%-110% occupancy)
- Likely declining (<100-80% occupancy)
- Strongly declining (<80% occupancy)
- Trend not established (species was too rarely encountered to establish a reliable trend)
Some species also have a conservation statement, indicating that species to be of particular conservation concern. In many cases, these are the species showing the most notable declining trends, but in other cases these statements are informed by other sources, such as the Breeding Bird Survey or the population surveys done for specific game and colonial species by the state Division of Fisheries & Wildlife. In a few cases, even increasing species have conservation statements – for example, Piping Plover is listed as “action/monitoring needed” because of its continued reliance on direct human protection in order to reproduce successfully. The conservation statements are:
- Conservation action urgent, or
- Continued action/monitoring needed
If there is no conservation statement, species with stable trends are recommended to be monitored to ensure stability; if the species is likely or strongly increasing, no action is recommended.
Any protected status (either at the state or federal level), or listing as a species of concern on the State Wildlife Action Plan, will also be indicated at the top of a species account.
Each account begins with a quote about the bird, often from historic ornithology literature but sometimes from farther afield, and a brief summary of its habits, its place in the Massachusetts avian community, and its apparent distribution trajectory as of Atlas 2. The Atlas does not include detailed natural history information for every species; for those who are interested, that information can be found in the first Massachusetts Breeding Bird Atlas.
History: This paragraph focuses on a species’ history in Massachusetts, with special attention paid to its historical breeding status, if known. For species that spread into Massachusetts during the time of the written record, some description will generally be given of the range expansion that led to its subsequent arrival. In many cases, species formerly bred in Massachusetts but were extirpated before Atlas 1; their stories will be detailed in this section.
Atlas 1: The third paragraph of each account details the species’ distribution in the state at the time of Atlas 1. These distribution summaries refer mainly to the various ecoregions, moving from west to east and calling out areas of particular concentration or noteworthy absence.
Atlas 2: The Atlas 2 summary for each species focuses mainly on how that species’ distribution has shifted in the state between the Atlases. When they are especially relevant, changes in the landscape that influence habitat availability are also discussed in this section.
Note: Not all species have a note, but, for those that do, there is some extra information available about the status of that species in the Commonwealth beyond what is provided by the Atlas. Sometimes there are notes explaining why the Atlas may over-represent or under-represent the range of a particular species. Notation of statistically significant Breeding Bird Survey trends are found in this paragraph, as well as notes on whether the species is showing statistically significant trends at larger regional scales in the Breeding Bird Survey. These regions, including the Eastern US Region and the New England/Mid-Atlantic Region, are defined by USGS, and the data from 1966 to 2011 were considered for each species. Other sources referenced in the note include surveys done by the Division of Fisheries & Wildlife and certain species-specific studies that have particular conservation implications for a given bird.