Weissenfluh Shawn, Kittilson Jeffrey, Gibbs Penelope, Reed Wendy L, Clark Mark E
Department of Biological Sciences, North Dakota State University, 1340 Bolley Drive, 201 Stevens Hall, Fargo, ND 58108-6050, USA.
Department of Microbiological Sciences, North Dakota State University, 1230 Albrecht Blvd, Fargo, ND 58108-6050, USA.
Conserv Physiol. 2025 Apr 11;13(1):coaf024. doi: 10.1093/conphys/coaf024. eCollection 2025.
Understanding individual variation in adult condition is necessary for developing hypotheses on how nest initiation, chick development and recruitment are related in many migratory birds. We quantified attributes of condition among Franklin's Gull () adults initiating nesting at different dates during the nesting period using four metrics: body measurements recorded from live-trapped birds, the corticosterone levels measured from blood samples collected serially from live-trapped birds, heterophil/lymphocyte ratios determined from blood smears and antimicrobial capacity of plasma. Variation in physiological condition was related to the timing of nesting such that individuals nesting later in the season had lower mass relative to skeletal size, increasing corticosterone concentrations measured 3-, 20- and 30-minute post-capture and reduced immune performance. Specifically, residual body mass decreased and keel bone exposure increased with laying date. Additionally, birds nesting later in the season show higher maximum corticosterone concentrations after exposure to acute capture stress along with reduced bacteria-killing capability of their plasma. Our findings indicate that timing of nesting is significantly related to the physiological condition of Franklin's Gull. Individual variation in condition may be related to time constraints observed in temperate latitudes and whether these birds are capital (i.e. acquiring resources outside the breeding area) or income (i.e. acquiring resources locally) breeders. Quantifying variation in physiological condition within the breeding season will aid in modelling population-level response to shifts in nesting phenology.
了解成年个体的状况差异对于提出许多候鸟筑巢开始、雏鸟发育和补充之间关系的假设至关重要。我们使用四个指标对在筑巢期不同日期开始筑巢的富兰克林鸥（）成年个体的状况属性进行了量化：从活体捕获的鸟类身上记录的身体测量数据、从活体捕获的鸟类身上连续采集的血样中测得的皮质酮水平、从血涂片确定的嗜异性粒细胞/淋巴细胞比率以及血浆的抗菌能力。生理状况的差异与筑巢时间有关，即季节后期筑巢的个体相对于骨骼大小体重较低，捕获后3分钟、20分钟和30分钟测得的皮质酮浓度增加，免疫性能降低。具体而言，随着产卵日期的推移，剩余体重下降，龙骨骨暴露增加。此外，季节后期筑巢的鸟类在暴露于急性捕获应激后显示出更高的最大皮质酮浓度，同时其血浆的细菌杀灭能力降低。我们的研究结果表明，筑巢时间与富兰克林鸥的生理状况显著相关。个体状况的差异可能与在温带地区观察到的时间限制以及这些鸟类是资本型（即在繁殖区域外获取资源）还是收入型（即在当地获取资源）繁殖者有关。量化繁殖季节内生理状况的差异将有助于模拟种群水平对筑巢物候变化的反应。
