Hi folks,

Just got the November 1996 volume (vol 49 No 6) of the Journal of Range =
Management, published by the Society for Range Management on a =
bi-monthly basis. Only one article in this issue that has anything to =
do with birds, from a study on BLM rangeland NE of Deming, N.M.

Sorry about those who receive this twice, I was told that it didn't go =
through the first time...

Jon. Anderson
Olympia, Washington
festuca at olywa.net


Wildlife numbers on excellent and good condition Chihuahuan Desert =
rangelands: An observation. Gretchen Smith, Jerry L Holocheck and =
Manual Cardenas. pp 489-493.

Abstract: "Information is lacking on the influence of range condition =
on wildlife populations in the Chihuahuan Desert. Wildlife observations =
were made along transects on ranges in excellent and good ecological =
condition in south-central New Mexico (86% and 72% of climax vegetation =
remaining, respectively). Black grama (Bouteloua eriopoda Torr.) =
dominated the excellent condition range, while the good condition range =
had a mixture of grasses, forbs, and shrubs. Plant species diversity was =
greater on the good compared to excellent condition range. Total mammal =
sightings/km2 during the study period were higher (P less than 0.05) on =
the good compared to excellent condition range. Sightings of important =
game species (scaled quail, mourning doves, pronghorn, desert =
cottontails) were higher on the good compared to excellent condition =
range. Lack of diversity in vegetation composition and structure appear =
to explain the lower wildlife sightings on the excellent condition =
range. Results from this study indicate that Chihuahuan Desert ranges in =
good ecological condition (51-75% of the climax vegetation) will better =
meet the needs of most wildlife species than ranges in climax or near =
climax range condition. Research shows grazing intensities that remove =
on average about 1/3 of current year's growth of key forage species =
(black grama) are effective in developing and maintaining range in good =
ecological condition in the Chihuahuan Desert."

The authors describe the methods they used, their results and then =
discuss the findings. They pointed out that the quail and doves were =
found mainly on the 'good' condition range, rather than the 'excellent' =
range - noting the use of invasive plants by these species which prefer =
earlier seral stages of the plant community.

"Based on the Shannon-Weaver index, wildlife diversity was greater on =
the good compared to excellent condition range (2.53 versus 1.19 =
respectively). This index is based on total number of species observed =
and proportion of each species within the total. Vegetational diversity =
was also greater on the good compared to excellent condition range (3.38 =
versus 2.72, repectively). Our data suggest that wildlife population =
diversity is positively correlated with vegetational diversity. However =
individual species of wildlife such as Cassin's sparrow (Aimophila =
cassinii Woodhouse) may use only those rangelands at or near the climax =
(Bock et al. 1984). Generally large tracts of rangeland in good overall =
condition will include areas in both higher and lower successional =
stages, and such mosaics can provide suitable habitat for nearly all the =
wildlife species that naturally occur in the area."

"We acknowledge that lack of replication is a limitation in our study. =
However opportunities to replicate this type of study on comparable =
sites large enough for meaningful data are restricted. The problem is =
that few large areas of excellent condition rangeland remain in the =
Chihuahuan Desert."

I think that the authors' statement, here, indicates that - contrary to =
their statements that "..climax conditions provide less than ideal =
habitat for many wildlife species in the Chihuahuan Desert, and lower =
seral stages with 55-75% remaining climax vegetation are suitable for =
maximizing wildlife species diversity." - the problem is that little =
"Excellent" condition range remains in this biogeographical area. =
"Fair" to "good" condition rangelands abound in most of the western =
shrub-steppe, and there is an awful lot of "Poor" condition range, as =
well. There is lots of habitat for cottontails and quail on the =
poorer-quality ranges, and the desert grassland species (such as the =
Cassin's Sparrow - let alone such grassland-obligate species as Aplomado =
Falcon, Masked Bobwhite, and Botteri's Sparrow to the west in =
Arizona...) *need* the better condition range - which is damned hard to =
find! I contend that we would be wiser to manage for excellent =
condition ranges - especially on the Public Lands - and realize that the =
majority of the range (with the fair to good condition...) will provide =
plenty of "diversity" for species that prefer the earlier seral stages.

Jon.