Pasture-scale vegetation predicts Dickcissel nest-site selection and success in native and exotic grass pastures

IF 2.6 2区 生物学 Q1 ORNITHOLOGY
Condor Pub Date : 2019-08-26 DOI:10.1093/condor/duz027
A. Monroe, L. Burger, J. Martin
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引用次数: 3

Abstract

ABSTRACT Exotic grasses such as bermudagrass (Cynodon dactylon) and tall fescue (Schedonorus arundinaceus) are widely established across the southeastern United States as livestock forage, but their structure and management can limit avian reproductive success. Native warm-season grasses (NWSG) are promoted as sustainable forage alternatives. To examine nesting suitability for tall structure specialists such as Dickcissels (Spiza americana) we established an operational-scale study in northeastern Mississippi, USA, with 4 treatments along a gradient of beef production intensity. Treatments included grazed exotic forages, 2 grazed NWSG treatments including Indiangrass (Sorghastrum nutans) monoculture and NWSG polyculture of Indiangrass, little bluestem (Schizachyrium scoparium), and big bluestem (Andropogon gerardii), and an ungrazed NWSG polyculture treatment. We monitored 208 Dickcissel nests in 2011 and 2012 to evaluate effects of treatment, vegetation structure, fire ants (Solenopsis spp.), and arthropod prey biomass on nest-site selection and nest survival. Survival rates varied among treatments and increased with pasture-scale visual obstruction reading (VOR), being lowest among grazed exotic grass, intermediate in grazed NWSG, and highest in ungrazed NWSG. Although Dickcissels selected nest sites with greater VOR, we found little support for effects of nest-site vegetation on survival. However, nest survival was lower for nests in shrubs that also occurred in pastures with greater shrub cover, and selection for shrubs declined as pasture-scale VOR increased, suggesting a functional response in selection. We found little support for food availability influencing nest survival. These results suggest NWSG pastures increase Dickcissel nest success through greater pasture-scale VOR by reducing Dickcissel selection of shrubs for nest sites, and possibly by reducing predator efficiency. Incorporating NWSG into beef production systems while maintaining availability of tall vegetation could benefit Dickcissels and other tall structure specialists.
牧场规模的植被预测Dickcissel筑巢地点的选择和成功在本地和外来牧草牧场
摘要:百慕大草(Cynodon dactylon)和高羊茅(Schedonorus arundinaceus)等外来牧草在美国东南部广泛用作牲畜饲料,但它们的结构和管理限制了鸟类的繁殖成功。原生暖季草(NWSG)被推广为可持续的饲料替代品。为了检查高结构专家如Dickcissels (Spiza americana)的筑巢适应性,我们在美国密西西比州东北部建立了一个操作规模的研究,沿牛肉生产强度梯度进行了4个处理。处理包括放牧外来牧草、放牧印度草(Sorghastrum nutans)和印度草、小蓝茎(Schizachyrium scoparium)和大蓝茎(Andropogon gerardii)的NWSG单栽培和NWSG复合栽培2个处理,以及不放牧NWSG复合栽培处理。2011年和2012年对208个Dickcissel巢穴进行了监测,评估了处理、植被结构、火蚁(Solenopsis spp.)和节肢动物猎物生物量对巢址选择和巢存活的影响。不同处理的存活率不同,随牧场尺度视觉障碍读数(VOR)的增加而增加,放牧的外来草的存活率最低,放牧的NWSG的存活率居中,未放牧的NWSG的存活率最高。虽然Dickcissels选择的巢址具有更高的VOR,但我们发现很少有证据支持巢址植被对生存的影响。然而,在灌木覆盖的牧场上筑巢的巢存活率较低,并且随着牧场尺度VOR的增加,对灌木的选择减少,这表明在选择中存在功能响应。我们发现很少有证据表明食物供应会影响巢穴的生存。这些结果表明,NWSG牧场通过减少Dickcissel对筑巢地点的灌木选择,并可能通过降低捕食者的效率,通过更高的牧场规模VOR增加Dickcissel筑巢成功率。将NWSG纳入牛肉生产系统,同时保持高植被的可用性,可以使Dickcissels和其他高结构专家受益。
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来源期刊
Condor
Condor ORNITHOLOGY-
CiteScore
6.30
自引率
12.50%
发文量
46
审稿时长
6-12 weeks
期刊介绍: The Condor is the official publication of the Cooper Ornithological Society, a non-profit organization of over 2,000 professional and amateur ornithologists and one of the largest ornithological societies in the world. A quarterly international journal that publishes original research from all fields of avian biology, The Condor has been a highly respected forum in ornithology for more than 100 years. The journal is one of the top ranked ornithology publications. Types of paper published include feature articles (longer manuscripts) Short Communications (generally shorter papers or papers that deal with one primary finding), Commentaries (brief papers that comment on articles published previously in The Condor), and Book Reviews.
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