||We assessed the impacts of hay management regimes on endemic grassland birds at Last Mountain Lake National Wildlife Area, Saskatchewan. Habitats included idle native grassland, nonnative hay mowed annually, and idle nonnative hay. We censused abundance of
territorial males from 1988 to 1991 and assessed reproductive success in 1991 and 1992 using a newly developed index of productivity. Baird’s sparrows( Ammodramus bairdii) and Sprague’s pipits (Anthuss pragueii) were the primarys pecies of conservation concern; these 2
species and savannah sparrows (Passerculus sandwichensis) occurred most commonly on our plots. Baird’s sparrow and Sprague’s pipits were most abundant in native habitat and generally least common on the idled hay fields, with intermediate numbers of these species
in annually mowed habitat. Savannah sparrows, however, were most common in the idle hay habitat and least common in annually mowed hay fields. Idle hay habitat mowed in 1988 had increased numbers of Sprague’s pipits and a higher frequency of western meadowlarks (Sturnella neglecta) the following year. However, Le Conte’s s parrows (Ammodramus leconteii), which had occurred only in idle hay fields, decreased the year after mowing. Inclement weather delayed hatching in 1991 such that <40% of songbird nests had fledged
by the last week of July, when mowing occurred. Productivity of savannahs parrows, the most abundant bird in the tame hay plots, declined by 80% following mowing. Mowing during the third week of July 1992 appeared to have less effect on productivity although Baird’s and savannah sparrow indexes declined (P= 0.01 and 0.07) in mowed fields. Almost 70% of nests had produced fledged young by the week of mowing, and offspring were thus less susceptible to the destruction of mowing. Although idle cultivated hay had higher productivity compared to mowed hay, it was generally less attractive to birds, particularly Baird’s sparrows and Sprague’s pipits, than was native vegetation. Thus, where it is desirable to keep
tracts of cultivated hay on wildlife lands, delaying mowing until 15 July or later will maintain habitat attractiveness for these and other endemic grassland species and allow adequate productivity
in years of normal breeding phenology. However, to provide habitat for those bird species that preferred the dense cover of idle hay and to further increase overall avian productivity, we recommend most individual fields be mowed only in alternate years and that
the remainder be left idle for a minimum of 3 years.