Yellow-headed (Xanthocephalus xanthocephalus) and red-winged (Agelaius phoeniceus) blackbirds coexist in marshes across North America. Pictured here at Iona Beach Regional Park in Vancouver, British Columbia, males of each species compete for nesting areas. In wetlands across their overlapping ranges, yellow-heads are dominant over red-wings, pushing them out of valuable marsh real-estate to secure the best nesting places.

Unfortunately, since the construction of Vancouver International Airport in 1968 and its expansion in subsequent years, both species have lost substantial extents of marsh habitat. Given their dominant–subordinate relationship, one might expect that habitat loss should disproportionately impact the subordinate red-wings, since they get last choice at nesting habitat, which might limit their reproductive success. Today, however, Iona Beach supports a healthy and abundant population of red-wings, and usually hosts only a few yellow-heads. Indeed, over the past half-century, the population of yellow-heads at Iona Beach has decreased ~95%, down from an estimated 70 individuals in 1970 to only 1–3 nowadays (Campbell RW, Dawe NK, McTaggart-Cowan I, et al. 2001. The Birds of British Columbia. Volume 4. Royal British Columbia Museum Victoria. Vancouver, Canada: UBC Press).

Despite their dominance, the yellow-headed blackbirds of Vancouver have seemingly been more negatively impacted by habitat loss and degradation than their subordinate red-winged cousins. Does their dominant behavior make yellow-heads more vulnerable to change? Are red-wings more tolerant of anthropogenic disturbances? Over the next decade, the potential extirpation of yellow-headed blackbirds from Iona Beach calls into question which blackbird genuinely is the dominant species. Of course, none of this stops the remaining few yellow-heads from bullying the abundant red-wings out of prime nesting space. At least population decline has not adversely impacted their yellow-headed ego!

黄头黑鸟（Xanthocephalus xanthocephalus）和红翅黑鸟（Agelaius phoeniceus）共存于北美各地的沼泽地中。照片摄于不列颠哥伦比亚省温哥华的爱奥那海滩地区公园，每个物种的雄性都在争夺筑巢区域。在其重叠范围的湿地中，黄头鹬比红翅鸬鹚占主导地位，将它们赶出宝贵的沼泽地，以确保最好的筑巢地点。

不幸的是，自 1968 年温哥华国际机场建成及其随后几年的扩建以来，这两个物种都失去了大量的沼泽栖息地。考虑到它们的主导-从属关系，人们可能会认为栖息地的丧失会对从属红翅鸟类产生不成比例的影响，因为它们在筑巢栖息地拥有最后的选择权，这可能会限制它们的繁殖成功率。然而如今，爱奥那海滩拥有健康且丰富的红翅鸟种群，通常只有少量黄头翅鸟。事实上，在过去的半个世纪中，爱奥那海滩的黄头鱼数量减少了约 95%，从 1970 年估计的 70 只减少到如今的仅 1-3 只（Campbell RW、Dawe NK、McTaggart-Cowan I、等人。2001 年。不列颠哥伦比亚省的鸟类。第 4 卷。维多利亚皇家不列颠哥伦比亚博物馆。加拿大温哥华：UBC 出版社。

尽管温哥华的黄头黑鸟占据主导地位，但它们似乎比它们的下属红翅近亲更容易受到栖息地丧失和退化的负面影响。他们的主导行为是否使黄头更容易改变？红翅雀更能忍受人为干扰吗？在接下来的十年里，爱奥纳海滩黄头黑鸟可能灭绝，这让人们质疑哪种黑鸟才是真正的优势物种。当然，这一切都无法阻止剩下的少数黄头鸟将大量的红翅鸟从主要的筑巢空间中夺走。至少人口减少并没有对他们黄头的自负造成负面影响！