Variation in mesopredator abundance and nest predation rate of the endangered Strange-tailed Tyrant Alectrurus risora

BROWNE, MELANIE; PASIAN, CONSTANZA; DI GIACOMO, ALEJANDRO G.; DI BITETTI, MARIO S.; DI GIACOMO, ADRIÁN S.

IBIS

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2023

0019-1019

Nest predation is the main cause of nestfailure in passerine birds and thus a key determinant of breeding traits. Accordingly,nest predator composition and abundance modulate nest predation rates. When toppredators are absent, mesopredator populations may become unchecked which inturn increases the predation pressure on their prey species. We evaluatedwhether nest predator abundance and breeding traits of an endangered grasslandbird, the Strange-tailed Tyrant Alectrurus risora, differed between two protectedareas: Iberá National Park (INP), where top predators have been extinct for 50years, and Reserva El Bagual (REB), where Pumas Puma concolor still havea stable population. We measured abundances of potential nest predator speciesand during the 2015–2018 breeding seasons we monitored Strange-tailed Tyrantnests and set camera traps to identify nest predators. Mesopredator abundancewas higher in INP, and foxes were identified as the main nest predators. Nestpredation rate was also higher in INP, where the daily nest predation rate and cumulativeprobability of nest predation were 0.05 ± 0.006 and 0.81, while in REB theywere 0.04 ± 0.004 and 0.70, respectively. The 10-times higher frequency of fox recordsin INP could explain the higher nest predation rate observed, suggesting thatthe extinction of top predators may increase nest predation rates of endangeredgrassland birds in protected areas through release of native mesopredatorspecies. The lower nest predation observed in REB was compensated by a highernest abandonment rate which resulted in a similar fledgling production in thetwo study sites. Clutch size, hatching success and number of nestlings did notdiffer between study sites. The lowbreeding success recorded for this endangered species despite its populationsbeing in protected areas of high conservation value is alarming given theglobal decline grassland bird populations are facing.@font-face{font-family:"Cambria Math";panose-1:2 4 5 3 5 4 6 3 2 4;mso-font-charset:0;mso-generic-font-family:roman;mso-font-pitch:variable;mso-font-signature:-536870145 1107305727 0 0 415 0;}p.MsoNormal, li.MsoNormal, div.MsoNormal{mso-style-unhide:no;mso-style-qformat:yes;mso-style-parent:"";margin:0cm;margin-bottom:.0001pt;mso-pagination:widow-orphan;font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:"Times New Roman";}.MsoChpDefault{mso-style-type:export-only;mso-default-props:yes;font-family:"Calibri",sans-serif;mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";mso-bidi-theme-font:minor-bidi;}div.WordSection1{page:WordSection1;}