Hi folks, =20

First of all, I want to apologize for sending a posting yesterday 3 =
times - I'm still getting used to the Microsoft Exchange email =
procedures.... :-p

I thought that some might be interested in this recent Wildlife =
Monograph published by The Wildlife Society. These monographs are =
papers that are lengthier, and more comprehensive than the usual 10-page =
journal articles.


Response of Nesting Ducks to Habitat and Management on the Monte Vista =
National Wildlife Refuge, Colorado. January, 1996. David W Gilbert, =
David R Anderson, James K Ringleman and Michael R Szmczak. Widl. Mono. =
No. 131. 44 pp.

ABSTRACT: We analyzed duck nesting data from the Monte Vista National =
Wildlife Refuge (MVNWR) in the San Luis Valley (SLV) of Colorado to =
evaluate the influence of habitat and management on nest density and =
success. From 1964 to 1990 (except 1977), 4154 duck nests were found on =
16,159 km (10,041 miles) of transect. Strip transects were searched =
twice annually, with a follow-up visit to nest sites to determine nest =
fate. During 1964-68, 521km (324 miles) of transect were searched (142 =
transects) twice each year, but this was reduced by half during 1969-90 =
(71 transects). We evaluated information on duck nests in 22 of 24 =
refuge management units. Mallards (Anas platyrhynchos) composed 54.5% =
of the duck nests on MVNWR, followed in abundance by teal species (A. =
cyanoptera, A. discors, A. crecca) and northern pintails (A. acuta). =
Refuge nest densities ranged from a low of 36 nests/km2 (93 nests/mi2) =
in 1979 to a high of 161 nests/km2 (418 nests/mi2) in 1973. Over the =
26-year period 1964-90, 52.4% of 4,154 nests were successful. Apparent =
annual nest success averaged 49.4% and ranged from 27% in 1978 to 72% in =
1966. Nest failure resulted from predation (25.8% of total nests), =
desertion (10.6%), flooding (4.9%) or unknown causes (10.8%). It was not =
possible to directly estimate true nest success, but indirect methods =
suggest that true nest success was 60 to 90% that of apparent nest =
success. Nest success rates were similar among species.
Baltic rush (Juncus balticus) was the most common vegetation on the =
refuge, followed in abundance by black greasewood (Sarcobatus =
vermiculatus), inland saltgrass (Distichlis stricta), and other grass =
species. Stands of common cattail (Typha latifolia), miscellaneous =
herbaceous vegetation, and Baltic rush were preferred nesting cover, =
whereas greasewood and saltgrass generally were avoided.
Nest density declined (P=3D0.037) with increasing grazing intensity, =
with large (38%) declines apparent the first season after only light =
grazing (0.2 animal unit month/ha [0.5 AUM/acre]). Three years after =
grazing, nest density was still depressed at least 17% below estimated =
pregrazing levels. In addition, nest success declined as grazing =
intensity increased (P =3D 0.070).
Duck nesting densities on the MVNWR are among the highest reported in =
North America. High duck production can be maintained by applying water =
in late March; reducing the frequency of grazing and burning treatments; =
and developing wetland management units to achieve their potential.


Long and lengthy post, but I found this to be an interesting paper. =
Especially in that the authors noted that the grazing/burning treatments =
of some refuge pastures removed nesting cover and resulted in low nest =
densities and nest success, which is common sense - yet the area had =
"among the highest nest densities reported in N America"! I guess we =
can always do better.... :-)

Jon. Anderson
Olympia, Wash
festuca at olywa.net