Long‐term population dynamics reveal that survival and recruitment of tropical boobies improve after a hurricane

Abstract

Variability in population numbers is a central issue in evolutionary ecology and also in biodiversity conservation. However, for most seabirds this information is lacking and tropical populations are virtually unstudied. Long-term studies are warranted because world's seabird populations exhibit an overall declining trend since 1950. Using data spanning 23 years, we investigated how adult survival, local recruitment, and their relative contributions to population growth (λ) vary over time in the blue-footed booby (Sula nebouxii), a long-lived locally foraging seabird that breeds in tropical waters. In addition, we investigated whether booby demographic rates exhibit the same declining trend observed in other seabirds, whether these rates are impacted by hurricanes, and whether these potential impacts differ between sexes. Our analysis of 4608 capture-recapture histories revealed that survival and recruitment were nearly equal between males and females, exhibited a declining trend over the last 23 years, and in both sexes, these vital rates improved after a hurricane. The declining trend in recruitment was slightly more attenuated in males. These results add to the current evidence for an overall declining trend in world's seabird populations and extend its confirmation to the warm eastern tropical Pacific. Moreover, they provide the first evidence that hurricanes may favor natural populations. As a result of the declining trend and variation in survival and recruitment, λ exhibited a slight decline and substantial variation over the 23 years. However, most λ values were equal to or higher than 1, and the long-term average indicates population increase. The ability of blue-footed boobies to maintain a positive population balance despite of negative trends in their vital rates might result from canalization of adult survival (the vital rate that contributes most to λ and shows lower variation compared to recruitment) against environmental variability.

Apparent absence of avian malaria and malaria-like parasites in northern blue-footed boobies breeding on Isla Isabel

“…Boobies breed mostly ~ 1.0–1.5 km away, at the wind-exposed northeastern end of the island, where we sampled them. The latter area is mainly covered by stunted garlic pear trees recurrently damaged by hurricanes 27 , 28 , and the hot and dry conditions there may limit the abundance and activity of potential vectors of blood parasites 6 , 23 , explaining the absence of blood parasites in our sample. In addition, the difference between boobies and frigatebirds in the prevalence of Haemoproteus parasites could be due to differences in the sampling years if parasites found two decades ago are no longer found in either species now.…”

Lack of age-related mosaic loss of W chromosome in long-lived birds

“…Blood samples were used to obtain genomic DNA. Blood samples were obtained in the booby colony of Isla Isabel (21° 52′ N, 105°54′ W), México, where monitoring of birds has been carried out annually since 1989 [ 29 , 30 ]; we sampled 61 females: 13 nestlings–fledglings (0–1 year), 19 young adults (2–7 years), 10 middle-aged adults (8–11 years) and 19 old adults (12–18 years). For the magnificent frigatebird, blood samples were obtained from a population on Isla Espiritu Santo, in Baja California Sur, México.…”

“…Adult populations of the blue-footed booby are slightly male-biased and those of F. magnificens are strongly male-biased (male/female ratios of greater than 1 and greater than 2, respectively; electronic supplementary material, figure S1) [ 26 – 28 ]. We studied a wild population of S. nebouxii off the Pacific coast of México that has been monitored over the past three decades and for which we know the exact age of individuals [ 29 , 30 ]. We also analysed data from nestlings and adults of the magnificent Frigatebird from a wild population in Baja California Sur, México.…”

Broad‐scale climate variation drives the dynamics of animal populations: a global multi‐taxa analysis

“…Twenty-five bird species including seabirds (e.g. albatross, penguins, shearwaters), New World warblers, a raptor and an owl showed associations with ENSO +/− in Canada, the USA, Mexico, North Atlantic, Selvagem Grande Island, French Sub-Antarctic Islands, Australia, New Zealand, and Antarctica (Peacock, Paulin & Darby, 2000;Wilson et al, 2001;Jenouvrier et al, 2005;Olivier et al, 2005;Seamans & Gutierrez, 2007;Kim et al, 2008;Sandvik, Coulson & Saether, 2008;Rolland et al, 2010;Boyle & Hone, 2012;Ramos et al, 2012;Pardo et al, 2013;McKellar et al, 2015;Humphries & Moller, 2017;Ancona et al, 2018;Cleeland et al, 2021). The frequency of dual associations was significantly different from that expected by chance alone, indicating that dual associations appeared to occur nonrandomly across species, taxonomic groups and geographical areas (G = 5.95, df = 1, p = 0.01).…”