Understanding habitat quality is central to understanding the distributions of species on the landscape, as well as to conserving and restoring at-risk species. Although it is well known that many species require different resources throughout their life cycles, pollinator conservation efforts focus almost exclusively on forage resources. In this study, we evaluate nesting habitat for bumble bees by locating nests directly on the landscape. We compared colony density and colony reproductive output for Bombus impatiens, the common eastern bumble bee, across three different land cover types (hay fields, meadows, and forests). We also assessed nesting habitat associations for all Bombus nests located during surveys to tease apart species-specific patterns of habitat use. We found that B. impatiens nested under the ground in two natural land cover types, forests, and meadows, but found no B. impatiens nests in hay fields. Though B. impatiens nested at similar densities in both meadows and forests, colonies in forests had much higher reproductive output. In contrast, B. griseocollis tended to nest on the surface of the ground and was almost always found in meadows. B. perplexis was the only species to nest in all three habitat types, including hay fields. For some bumble bee species in this system, meadows, the habitat type with abundant forage resources, may be sufficient to maintain them throughout their life cycles. However, B. impatiens might benefit from heterogeneous landscapes with forests and meadows. Results for B. impatiens emphasize the longstanding notion that habitat use is not always positively correlated with habitat quality (as measured by reproductive output). Our results also show that habitat selection by bumble bees at one spatial scale may be influenced by resources at other scales. Finally, we demonstrate the feasibility of direct nest searches for understanding bumble bee distribution and ecology.

中文翻译：

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土地覆盖对大黄蜂筑巢栖息地利用和繁殖产量的对比影响

了解栖息地质量对于了解景观中物种的分布以及保护和恢复濒危物种至关重要。尽管众所周知，许多物种在其整个生命周期中需要不同的资源，但传粉媒介保护工作几乎只专注于草料资源。在这项研究中，我们通过直接在景观上定位巢穴来评估熊蜂的筑巢栖息地。我们比较了三种不同土地覆盖类型（干草田、草地和森林）中常见的东部熊蜂Bombus impatiens 的菌落密度和菌落繁殖产量。我们还评估了调查期间位于的所有Bombus巢穴的筑巢栖息地关联，以梳理特定物种的栖息地使用模式。我们发现凤仙花在地下两种自然土地覆盖类型森林和草地中筑巢，但在干草田中没有发现凤仙花筑巢。尽管凤仙花在草地和森林中以相似的密度筑巢，但森林中的群体具有更高的繁殖产量。相比之下，B. griseocollis倾向于在地面筑巢，几乎总是在草地上发现。B. perplexis是唯一在所有三种栖息地类型（包括干草田）中筑巢的物种。对于这个系统中的一些熊蜂物种，草甸，草料资源丰富的栖息地类型，可能足以维持它们的整个生命周期。然而，凤仙花可能受益于森林和草地的异质景观。凤仙花的结果强调了长期以来的观点，即栖息地利用并不总是与栖息地质量（以繁殖产出衡量）呈正相关。我们的结果还表明，熊蜂在一个空间尺度上的栖息地选择可能会受到其他尺度资源的影响。最后，我们证明了直接搜索巢穴以了解熊蜂分布和生态的可行性。