Conservation of breeding grassland birds requires local management strategies when hay maturation and nutritional quality differ among regions

Abstract

Early hay harvest can negatively affect grassland bird reproduction. Agriculturists may delay harvest in support of grassland bird conservation if hay quality is not jeopardized. We examined changes in hay quality over time at three latitudes in Ontario, and for the central region, we related results to bobolink (Dolichonyx oryzivorus) breeding phenology. We collected hay samples at all latitudes from 1 June through 16 July and quantified changes in percent crude protein (CP), acid detergent fibre (ADF), calcium (Ca) and phosphorus (P). At the same time, we also monitored breeding behaviour of all grassland birds but sufficient data for analyses and comparative purposes were collected only for bobolinks in central Ontario. Most Ontario hayfields sampled were low in energy and digestibility throughout the growing season (mean ADF values>35%). Ca levels were more than adequate for most livestock but P supplementation may be required depending on the production goals of the farmer. Crude protein levels were higher in forage samples collected from northern study plots and fell below 10% one week later than in central and southern Ontario. In central Ontario, CP levels were highest in the first week of June (12–15%). In the last two weeks of June through to mid-July, mean CP levels dropped from 11% to 9.5%, roughly 0.5% per week. Fledgling bobolinks were first observed on 14 and 16 June; they were counted in larger numbers after 20 June and reached a peak 1–14 July. A delayed hay harvest (mid-July) in this region would support bobolink reproduction without compromising forage quality for a variety of livestock enterprises. Timing of hay harvest to benefit grassland birds in regions to the north and south may differ depending on local geologic and climatic conditions and breeding bird behaviour. Based on our results, farmers that opt to manage their hayfields in support of grassland birds can delay the timing of hay harvest with trade-offs not as severe as once thought. The delayed hay harvest strategy may have wider applications to agro-ecosystems globally; its feasibility would only require knowledge of local breeding bird activity and forage quality over time.