Department of Ecology and Evolutionary Biology, Cornell University and Cornell Lab of Ornithology, 159 Sapsucker Woods Road, Ithaca, NY, 14850, USA.
Oecologia. 2023 Dec;203(3-4):277-296. doi: 10.1007/s00442-023-05448-0. Epub 2023 Sep 29.
After an overview of the discussion about the existence of intra- and interspecific competition that illustrates the contradictory opinions I conclude that long-term field experiments are needed for firm conclusions. I discuss in some detail the role of two factors that limit population size of secondary cavity nesting birds e.g. territorial behavior and adequate cavities. This is followed by an overview of experimental long-term field studies in Belgium showing that intra- and interspecific competition in a great tit-blue tit system exists. By using nestbox configurations with high densities of nestboxes that differ in the diameter of their entrance hole in replicate study plots it is possible to manipulate the breeding densities of great tit Parus major and blue tit Cyanistes caeruleus independently, thereby varying the intensity of intra- and interspecific competition between these two coexisting species. When blue tit densities are experimentally increased local recruitment of great tits increases, and adult great tit post-breeding dispersal to other study plots decreases, implying that great tits use blue tit density to evaluate habitat quality and that high blue tit density results in heterospecific attraction. The reverse is not true. An experimental increase in great tit density leading to an increase in interspecific competition in a plot where blue tit density was already high leads to a decrease in blue tit nestling mass (illustrating interspecific competition for food), but to a gradual increase in blue tit body size. Both are primarily caused by an increase in the body size of immigrants (caused by intraspecific competition for protected roosting holes) in contrast to the control plot, where neither is observed. I also summarize behavioral, ecological and possible evolutionary effects of sparrowhawks on blue tits after sparrowhawks settled in an isolated study plot halfway through the study: adult survival substantially decreased for both sexes, but more for females that laid large clutches, leading to selection for females that laid a smaller clutch. This led to a change in the reproduction/survival life-history trade-off. Adult winter weights and nestling weights decreased, and the heaviest fledglings were selected against. Furthermore the frequency of polygyny increased. The long-term experiments also document the role of the use of public information and that species that compete can be attracted to sites in which competitor density is high.
在概述了关于种内和种间竞争存在的讨论之后，该讨论说明了我得出的矛盾观点，即需要进行长期的实地实验才能得出确定的结论。我详细讨论了限制次生洞穴筑巢鸟类种群大小的两个因素的作用，例如领地行为和足够的洞穴。接下来概述了在比利时进行的长期野外实验研究，这些研究表明，大山雀-蓝山雀系统中存在种内和种间竞争。通过在重复研究地块中使用具有不同入口孔直径的巢箱配置，可以独立地操纵大山雀 Parus major 和蓝山雀 Cyanistes caeruleus 的繁殖密度，从而改变这两个共存物种之间的种内和种间竞争强度。当蓝山雀的密度通过实验增加时，当地大山雀的招募增加，而繁殖后的成年大山雀向其他研究地块的扩散减少，这表明大山雀使用蓝山雀的密度来评估栖息地的质量，并且高蓝山雀密度导致异种种群吸引。反之则不然。在蓝山雀密度已经很高的一个地块中，实验增加大山雀的密度导致种间竞争加剧，这会导致蓝山雀雏鸟的体重减轻（表明种间竞争是为了争夺食物），但蓝山雀的体型逐渐增大。这两者主要是由于移民（由于对受保护的栖息洞的种内竞争而引起）的体型增大引起的，而对照地块则没有观察到这一点。我还总结了在研究进行到一半时，雀鹰在一个孤立的研究地块中定居后对蓝山雀的行为、生态和可能的进化影响：两性的成年存活率都大大降低，但产卵量较大的雌性降低更多，这导致选择产卵量较小的雌性。这导致了繁殖/生存生活史权衡的变化。成年冬季体重和雏鸟体重下降，体重最重的幼鸟被淘汰。此外，多配偶制的频率增加。长期实验还记录了使用公共信息的作用，以及可以竞争的物种可以被吸引到竞争者密度高的地方。
