Chapter 3 Avifaunal and Habitat Analysis
In preparing this Bird Conservation Plan for New Mexico, New Mexico Partners in Flight has followed the two step process of species assessment and prioritization developed by Partners in Flight (see Punjabi 2001 and the Partners in Flight Continental Plan, Rich et al. 2004). In this context, species assessment refers to the process of evaluating the biological vulnerability and conservation status of each species, through the application of a standardized scoring system; species prioritization refers to the use of assessment data to determine conservation priorities for the state. Thus, the assessment process produces a database of vulnerability scores, while prioritization produces a list of species of conservation concern, which may be further subdivided using various criteria. In general, New Mexico Partners in Flight has closely followed national Partners in Flight guidelines, with some modifications to reflect state interests and concerns.
The Partners in Flight assessment process is based on a series of biologically-based measures of conservation vulnerability. For each species in the planning area, a numerical score from one (lowest vulnerability) to five (highest vulnerability) is assigned for each measure. Methods and criteria for scoring have been continually tested, reviewed, and refined since the Partners in Flight species assessment process was first developed in 1991, and the scientific credibility of the system has been acknowledged by the American Ornithologists’ Union (Bissinger et al. 2000).
For the purpose of species prioritization, a variety of measures or “vulnerability factors” are considered. Some of these (breeding distribution, non-breeding distribution, and population size) are assessed “globally”, meaning they convey information about the entire species population. Others (threats to breeding populations and habitats, threats to non-breeding populations and habitats, population trend, and local area importance) may be assessed for particular geographic regions. This plan uses global and North American scores for landbirds developed by Partners in Flight and maintained in the Partners in Flight Global Scores Database; comparable scores for shorebirds, water birds and waterfowl are drawn from national plans for these taxa; and local (state or regional) scores for threat to breeding, population trend, and area importance are assigned by New Mexico Partners in Flight.
Vulnerability factors used in this plan, along with abbreviations and brief descriptions, are listed in Table 3.1 below. Additional details and specific scoring criteria for each measure are provided in Appendix B.
Table 3.1 Vulnerability factors used in species assessment
|Vulnerability Factor||Description or Criteria|
|1||Distribution (the greater of the 2 following distribution scores)|
|Global Breeding Distribution||PIF continental species assessment|
|Global Non-breeding Distribution||PIF continental species assessment|
|2||Threats (the greatest of the 3 following threat scores)|
|Breeding Season Threats in North America||PIF continental species assessment|
|Non-breeding Season Threats||PIF continental species assessment|
|Breeding Season Threats in New Mexico||NMPIF state species assessment|
|3||Global Population Size||PIF continental species assessment|
|4||Local Population Trend (state or regional)||NMPIF state species assessment, using Breeding Bird Survey data|
|5||Importance of New Mexico to Breeding||NMPIF state species assessment, based on distribution and PIF state population estimates|
In assessing vulnerability due to distribution, only the higher of the two (breeding and non-breeding distribution) global assigned scores is counted. In assessing vulnerability due to threats, only the highest of three (breeding in North America, breeding in New Mexico, and non-breeding) assigned scores is counted. This results in a set of five scoring factors for assessing vulnerability. This system is in general agreement with that adopted by Partners in Flight for species assessment nationally.
Scores for all five factors may be summed to produce a combined score that represents a single, overall metric of conservation vulnerability. Combined scores for New Mexico birds have been calculated as follows:
Combined Score = Distribution + Threats + Global Population Size + Local Population Trend + Importance of New Mexico to Breeding
Note that by this five-variable formula, the maximum possible combined score is 25 and the minimum score is 5.
New Mexico Partners in Flight has chosen to present its high priority species in two broad categories, which are further sub-divided according to degree of vulnerability.
Conservation prioritization in a state, or other management unit, may be driven by two equally important concepts. Contributing to overall species conservation, in the state and larger continental context, and contributing to maintaining state biodiversity are distinct components of the New Mexico Partners in Flight plan, and it is often difficult to prioritize between the two.
For example, many breeding species occur only as very small, peripheral populations in the state. Such species receive a low score of 1 for the vulnerability factor “Importance of New Mexico to Breeding”. In most cases, these are species for which Partners in Flight estimates that New Mexico supports less than one percent of the total breeding population. While the overall conservation status of such species may not be greatly affected by actions undertaken in New Mexico, maintaining breeding populations of these species is considered to be extremely important from a state biodiversity perspective.
To recognize and address this challenge, New Mexico Partners in Flight presents lists of species of overall conservation concern under Species Conservation (SC) and species of concern in maintaining state biodiversity under Biodiversity Conservation (BC). Within each of these two lists, species are categorized into two levels of vulnerability (Table 3.2 below). Level 1 includes species of high conservation concern in either the SC or BC category (SC1 and BC1, respectively). For the most part, these are species facing moderate to severe threats and showing unknown or declining local population trends. They are considered to be species in need of immediate conservation action. Level 2 species are considered to be of moderate or potential conservation concern in either the SC or BC category (SC2 and BC2, respectively). They show some signs of vulnerability, and may warrant careful monitoring. The Species Conservation and Biodiversity Conservation categories are established based on the vulnerability factor “Importance of New Mexico to Breeding”. The species under Species Conservation are ranked as level 1 or level 2 based on the Combined Scores (greater than 16 for level 1 and 15 or 16 for level 2). Species with a slightly lower Combined Score of 14 still qualify as level 2 if they have moderate to high state-based vulnerability, as reflected in “Breeding Season Threats in New Mexico” and “Local Population Trend” scores. Species under Biodiversity Conservation are ranked as level 1 or level 2 according to the degree of threat they face in New Mexico, as indicated by “Breeding Season Threats in New Mexico” scores; however, those with Combined Scores of 11 or less are excluded.
Table 3.2 Criteria for priority listings
|Species Conservation||SC1||Importance of New Mexico to Breeding > 1 and|
|Level 1||Combined Score > 16|
|Species Conservation||SC2||Importance of New Mexico to Breeding > 1 and|
|Level 2||Combined Score = 15 or 16 or|
|Importance of New Mexico to Breeding > 1 and|
|Combined Score = 14 and|
|Breeding Season Threats in New Mexico + Local Population Trends > 5|
|Biodiversity Conservation||BC1||Importance of New Mexico to Breeding = 1 and|
|Level 1||Breeding Season Threats in New Mexico > 3|
|Biodiversity Conservation||BC2||Importance of New Mexico to Breeding = 1 and|
|Level 2||Breeding Season Threats in New Mexico = 3 and Combined Score > 11|