In response to our recent paper (Drymon et al. 2019), Yosef (2019) questions the mechanism proposed to explain interactions between tiger sharks (Galeocerdo cuvier) and migratory songbirds, while offering an alternative mechanism based on a single observation. We appreciate the comments from Yosef and the opportunity to respond

Drymon, J. Marcus

Feldheim, K.

Fournier, A. M.V.

Jefferson, A. E.

Kroetz, A. M.

Powers, Sean P.

Seubert, E. A.

English

University of South Alabama Institutional Repository

University of South Alabama JagWorks@USA University Faculty and Staff Publications 2019 Tiger Sharks Eat Songbirds: Reply J. Marcus Drymon K. Feldheim A. M.V. Fournier A. E. Jefferson A. M. Kroetz See next page for additional authors Follow this and additional works at: https://jagworks.southalabama.edu/usa_faculty_staff_pubs  Part of the Aquaculture and Fisheries Commons, Biology Commons, Marine Biology Commons, Ornithology Commons, Other Ecology and Evolutionary Biology Commons, Population Biology Commons, and the Terrestrial and Aquatic Ecology Commons Authors J. Marcus Drymon, K. Feldheim, A. M.V. Fournier, A. E. Jefferson, A. M. Kroetz, Sean P. Powers, and E. A. Seubert Tiger sharks eat songbirds:replyJ. M. DRYMON,1,2,7 K. FELDHEIM,3 A. M. V. FOURNIER,1,4E. A. SEUBERT,1 A. E. JEFFERSON,1,2 A. M. KROETZ,5 ANDS. P. POWERS6Citation: Drymon, J. M., K. Feldheim, A. M. V. Fournier, E. A.Seubert, A. E. Jefferson, A. M. Kroetz, and S. P. Powers. 2019.Tiger sharks eat songbirds: reply. Ecology 100(11):e02870. 10.1002/ecy.2870In response to our recent paper (Drymon et al. 2019),Yosef (2019) questions the mechanism proposed toexplain interactions between tiger sharks (Galeocerdocuvier) and migratory songbirds, while offering an alter-native mechanism based on a single observation. Weappreciate the comments from Yosef and the opportu-nity to respond.Yosef (2019) questions two aspects of the mecha-nism we suggested. First, he states that “the frequencyand scale of inclement weather in fall is not consistentor regular between years.” To this first point, we dis-agree. For small migratory birds, inclement weatherevents include cold fronts, rain, mist, or adversewinds (Newton 2007), which are sufficiently commonin the northern Gulf of Mexico during the fall.Moreover, we found that tiger shark/bird interactionswere common from year to year, occurring in everyyear (nine total) we examined tiger shark stomachcontents. We also found that the interaction was notstrictly limited to a few individuals; nearly 40% ofthe tiger sharks we examined had avian remains intheir stomachs.Second, Yosef (2019) states that “although a relativelylarge portion of the avian migrants do not complete theirmigration, it usually does not occur immediately afterleaving landfall.” To this second point, we disagree.Although it was initially surprising that these interac-tions were more common in the fall compared to spring(and thus taking place closer to the migratory departurelocation rather than the migratory destination), we areconfident that the mechanism we have proposed (adverseweather in the fall) is sufficient rationale. During fallmigration, young-of-the-year birds are traveling southon their first migration and are likely to overshoot intothe Gulf of Mexico at night, before correcting and tryingto return to land. If they do not realize they have over-shot soon enough, or they experience adverse weatherwhen they do turn around, they would be highly likelyto either exhaust themselves, fall into the water and dieof exposure, or exhaust themselves and die before reach-ing the water.Yosef (2019) goes on to suggest behavioral thermoreg-ulation may explain the interaction between tiger sharksand terrestrial birds, and suggests we try and “correlate(our) data with species abundance but also with inclementweather, especially heat waves.” The account of behav-ioral thermoregulation in European Bee-eaters (Meropsapiaster, Yosef 2010) is interesting and may provide anexplanation for the occurrence of a Bee-eater from a sin-gle tiger shark stomach (Yosef et al. 2002); however,behavioral thermoregulation is highly unlikely to explainthe interactions reported in Drymon et al. (2019), forthe following reasons.First, there are dramatic differences in climatebetween the two study areas in question: the northernGulf of Mexico (Drymon et al. 2019) and the northernRed Sea (Eilat, Israel; Yosef et al. 2002). For example,the average fall temperatures in the northern Gulf ofMexico are less than 31°C, compared to 43°C andgreater in the northern Red Sea. Perhaps more impor-tantly, the climate in the northern Gulf of Mexico isextremely humid, compared to the khamsins describedby Yosef (2010), which are hot, dry winds. Therefore, theevaporative cooling evoked in Yosef (2010) would beimpossible in the humid climate of the northern Gulf ofMexico.Second, we found no evidence in the literature ofbehavioral thermoregulation for any of the migratoryspecies in our area; we interpret this to mean the behav-ior described in Yosef (2010) may be unique to EuropeanBee-eaters in Eilat, where small, shallow (i.e., 20 cm),predator-free salt ponds are available, unlike the north-ern Gulf of Mexico.Manuscript received 10 July 2019; accepted 24 July 2019.Corresponding Editor: John Pastor.1 Coastal Research and Extension Center, Mississippi StateUniversity, 1815 Popps Ferry Road, Biloxi, Mississippi 39532USA2Mississippi–Alabama Sea Grant, 703 East Beach Drive,Ocean Springs, Mississippi 39564 USA3Pritzker Laboratory for Molecular Systematics and Evolu-tion, Field Museum, 1400 South Lake Shore Drive, Chicago,Illinois 60605 USA4Forbes Biological Station–Bellrose Waterfowl ResearchCenter, Illinois Natural History Survey, Prairie Research Insti-tute, University of Illinois at Urbana-Champaign, Havana, Illi-nois 62644 USA5National Marine Fisheries Service, Southeast FisheriesScience Center, Riverside Technology, Inc. 3500 Delwood BeachRoad, Panama City Beach, Florida 32408 USA6Department of Marine Sciences, University of South Ala-bama, 5871 USA Drive North, Mobile, Alabama 36688 USA7E-mail: marcus.drymon@msstate.eduArticle e02870; page 1CommentsEcology, 100(11), 2019, e02870© 2019 by the Ecological Society of America 19399170, 2019, 11, Downloaded from https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.2870 by University Of South Alabama, Wiley Online Library on [26/10/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons LicenseThe feeding habits of tiger sharks are truly extraordi-nary. Over half a century ago, a single yellow-billedcuckoo (Coccyzus americanus) was found in the stomachof a tiger shark (Saunders and Clark 1962). The authorssuggested the bird was a fallen migrant, a mechanismechoed by Dodrill and Gilmore (1977). Since then, incle-ment weather (Carlson et al. 2002, Gallagher et al.2011) and behavioral thermoregulation (Yosef 2010) hasalso been advanced to explain the presence of terrestrialbirds in the stomachs of tiger sharks. Intuitively, theways in which tiger sharks encounter terrestrial birds arelikely context dependent. However, based on the prepon-derance of tiger shark stomachs containing bird remains(41 of 105 examined) collected over a 9-yr period, wemaintain that the most parsimonious explanation forthe prevalence of migratory birds in the diets of tigersharks in the northern Gulf of Mexico is the mechanismproposed in Drymon et al. (2019).LITERATURE CITEDCarlson, J. K., M. A. Grace, and P. K. Lago. 2002. An observa-tion of juvenile tiger sharks feeding on clapper rails off thesoutheastern coast of the United States. Southeastern Natu-ralist 1:307–310.Dodrill, J. W., and R. G. Gilmore. 1977. Land birds in the stom-achs of tiger sharks Galeocerdo cuvier (Peron and Lesueur).Auk 95:585–586.Drymon, J. M., K Feldheim, A. M. V. Fournier, E. A. Seubert,A. E. Jefferson, A. M. Kroetz, and S. P. Powers. 2019. Tigersharks eat songbirds: scavenging a windfall of nutrients fromthe sky. Ecology 100:e02728.Gallagher, A. J., T. Jackson, and N. Hammerschlag. 2011.Occurrence of tiger shark (Galeocerdo cuvier) scavengingon avian prey and its possible connection to large-scalebird die-offs in the Florida Keys. Florida Scientist74:264–269.Newton, I. 2007. Weather-related mass-mortality events inmigrants. Ibis 149:453–467.Saunders, G. B., and E. Clark. 1962. Yellow-billed cuckoo instomach of tiger shark. Auk 79:118.Yosef, R. 2010. Unusual thermoregulatory behavior in migra-tory European Bee-eaters (Merops apiaster). Wilson Journalof Ornithology 122:378–380.Yosef, R. 2019. Tiger sharks eat songbirds: Comment.Yosef, R., D. Zakai, M. Rydberg-Heden, and R. Nikolajsen.2002. An unusual record of a European Bee-eaterMerops api-aster from Eilat—inside a tiger shark Galeocerdo cuvier. Sand-grouse 24:140–142.Article e02870; page 2 COMMENTS Ecology, Vol. 100, No. 11 19399170, 2019, 11, Downloaded from https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.2870 by University Of South Alabama, Wiley Online Library on [26/10/2022]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

Tiger Sharks Eat Songbirds: Reply

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