Survival of Sooty Falcons (Falco concolor) breeding in Oman

Abstract

Although the Middle East supports a high level of avian biodiversity, the ecology of relatively few species that use the region has been studied in detail. Despite its restricted breeding distribution in the Middle East, and apparent unfavorable conservation status, little is known about the population ecology of the Sooty Falcon (Falco concolor), one of only two falcon species that breeds in the boreal summer. We applied multi-state models to capture–mark–recapture data collected during 2007–2014 in the Sultanate of Oman to estimate, for the first time, the probabilities of capture, age-specific breeding probabilities, and state-specific apparent survival for Sooty Falcon. Capture probability for breeding adults (±1SE) was 0.443 ± 0.088. Annual apparent survival probability for pre-breeders and for breeding adults was 0.570 ± 0.048 and 0.656 ± 0.069, respectively. The probability that 2-, 3-, and 4-year-old falcons returned as breeders was 0.065 ± 0.036, 0.159 ± 0.069, and 0.339 ± 0.211, respectively. In 2013, we radio-tagged five fledgling falcons, and monitored their fates using satellite-based tracking. All initiated their first migration and survived for 48 days following radio-tagging, but four of the five birds died by 70 days post-tagging; only one survived >100 days. Our results suggest that only about 12 % of fledglings survive to the average age of first breeding (~3.8 years), and that most of first-year mortality occurs during their first migration or soon after they reach their destination. Low apparent survival of pre-breeders could result in low recruitment to the breeding population, and population declines. A comprehensive population-level assessment is urgently needed to accurately determine the status of Sooty Falcons, and to devise flyway-scale conservation plans.

Zusammenfassung

Überlebenschance von brütenden Schieferfalken ( Faclo concolor ) im Oman

Obwohl es im Nahen Osten ein hohes Maß an Artenvielfalt gibt, wurden in dieser Region nur relativ wenige Arten untersucht. So wissen wir trotz der eingeschränkten Brutverteilung im Nahen Osten und dem ungünstigen Schutzstatus wenig über die Populationsökologie des Schieferfalken (Falco concolor), eine von zwei Falkenarten, die dort im borealen Sommer brüten. Wir sammelten Fang-/Wiederfang-Daten im Sultanat von Oman von 2007–2014. Wir verwendeten multi-state models, um Fangwahrscheinlichkeit, altersspezifische Brutwahrscheinlichkeit und Überlebenschance des Schieferfalken zu schätzen. Die Fangwahrscheinlichkeit für brütende adulte Schieferfalken betrug 0,443 ± 0,088 (±1 SE). Die jährliche Überlebenswahrscheinlichkeit für immature Vögel war 0,570 ± 0,048, die für adulte Brutvögel 0,656 ± 0,069. Die Wahrscheinlichkeiten, dass 2-, 3-, und 4-jährige Falken als Brutvögel zurückkommen, betrugen 0,065 ± 0,036, 0,159 ± 0,069 bzw. 0,339 ± 0,211. 2013 haben wir fünf junge Falken mit Satellitensendern ausgestattet. Alle begannen ihren ersten Zug und überlebten die ersten 48 Tage nach der Besenderung. Vier von fünf Vögeln starben jedoch innerhalb von 70 Tagen nach der Besenderung. Nur einer überlebte für mehr als 100 Tage. Unsere Ergebnisse zeigen, dass nur etwa 12 % der Jungvögel bis zum Durchschnittsalter von Erstbrütern (~3.8 Jahre) überleben und dass die höchste Sterberate im ersten Jahr während der ersten Migration auftritt oder kurz, nachdem die Vögel ihr Ziel erreicht haben. Die niedrige Überlebensrate von immaturen Vögeln könnte zu einem geringen Recruitment in die Brutpopulation führen und somit zu einem Rückgang der Population. Eine umfassende Studie des Schieferfalken ist dringend notwendig, um seinen genauen Schutzstatus zu bestimmen und Schutzmaßnahmen für die Zeit der Wanderung zu entwickeln.

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Acknowledgments

Financial support was provided by the Office for Conservation of the Environment Diwan of Royal Court (OCE), Natural Research, Ltd., UK, Petroleum Development Oman and the Environment Society of Oman. In-kind and logistical support was provided by the Royal Yachts of Royal Court Affairs and the Ministry of Environment and Climate Affairs (MECA). Research permits for the Daymaniyat Islands were kindly provided by MECA, and permission to land on Fahal Island by the Royal Oman Police. We would particularly like to thank the captains and crew of the “Al Noores” and the MECA rangers for their hospitality and logistical support. The Environment Society of Oman provided some PIT tag reading equipment. Many individuals were very helpful including: Y. Al-Salami, A. Spalton, M. Al-Balushi, A. Al-Owisi, N. Al-Sharji, A. Al-Amri, A. Al-Raisi, J. Knapp, A. Al-Kyumi, F. Al-Lamki, K. Am Busaidi, M. Hearst, R. Eaton, M. Nicoll, A. Thorpe, M. Gschweng, L. Arison and G. Razafimanjato. A. Al-Raisi provided GIS support. The help provided by Said Al-Sayabi of the Royal Yachts was vital to the success of the work. The manuscript was greatly improved by the comments of two anonymous referees. Finally, we are immensely grateful to James D. Nichols for much needed guidance in data analysis. The work was performed in accordance with the laws of the Sultanate of Oman.

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Correspondence to M. J. McGrady.

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Communicated by C. Barbraud.

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McGrady, M.J., Al Fazari, W.A., Al Jahdhami, M.H. et al. Survival of Sooty Falcons (Falco concolor) breeding in Oman. J Ornithol 157, 427–437 (2016). https://doi.org/10.1007/s10336-015-1302-6

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Keywords

  • State-specific survival
  • Age-specific breeding probability
  • Capture–mark–recapture analysis
  • Falco concolor
  • Sooty Falcon demography
  • Multi-state models
  • Sultanate of Oman