Bird Record Trends: What Can We Learn From Bird 

 Distribution Information? 



This edition is a 'snapsiiot' of tiie Montana Bird Distribution database at a single point in time 

 ( 1 January 2003). It is useful in se\eral ways because it: 



• Displays the range and status of each species in Montana; 



• Can help with bird identification; 



■ Can alert birders to areas of die state that are poorly covered or to species that ai-e insufficiendy 

 reported. 



The database is pt)tentially much more useful, however, because it can provide information 

 important to the conservation of Montana's avitauna. The simplest and most important examples of 

 this are c]ueries of the database designed to answer questions about "trends": which species appear to be 

 increasing in numbers or range or both, and which appear to be decreasing, and where the changes are 

 occurring. 



However, the usefulness of such queries is compromised because the database does not represent 

 w here birds actually are, but rather where birds have been observed and reported. Nevertheless, it is 

 useful to query for trend information and to publish those results, since the information can suggest 

 species or areas of the state that need more attention and might nn)ti\ate birders to report more 

 observations of those species and in those areas. 



We present some examples of trend information based on queries of the Montana Bird DistribuUon 

 database. Two kinds of queries were run: 



( 1 ) queries to discern trends for species are reported as lists of "increasers" and "decreasers"; 



(2) queries for QLL richness trends are reported using maps. 



Both kinds of queries are based on the following protocol: 

 ■ Only QLL records are used ( 73,054 records) 

 • Records arc broken into 3 time periods 

 ° PI =pre 1994(23,566) 

 ° ?2 = 1994 through 1997 (27,293) 

 ° P3 = 1998 through 2002 (22,195) 

 (NOTE: these dates were selected because the number of records for each of these periods is similar. 

 No corrections were made for actual difference in numbers of observations among the periods.) 



Species Trends 



For species trends, we first calculate how many QLLs each species has been reported in during 

 each time period. We then define "increasers" as those species for which PI -QLLs < P2-QLLs < P3- 

 QLLs (where "Pl-QLLs" is the number of QLLs where that species was reported before 1994, etc.) 

 Similarly, "decreasers" have Pl-QLLs > P2-QLLs > P3-QLLs. 



Species Richness and Trends by QLL 



For QLL/species richness trends, we first calculate how many species have been reported in each 

 QLL during each period. Then "increasers" are those QLLs for which PI -species < P2-species < P3- 

 species (where "Pl-species" is the number of species reported in that QLL before 1994, etc.) 



Reported Observations and Trends by QLL 



Finalh', we present a QLL map that summarizes the total number t)f reported observations, and 

 the trends across the 3 periods, for each QLL. Comparing this map with the "species richness" map 

 suggests that many, but not all, ot the trends seen in species richness mav simply reflect trends in the 

 number of reported observations. 



