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Revista Brasileira de Ornitologia 27(2): 126–128. SHORT-COMMUNIC ARA TICLE TION June 2019 Waterbirds catch and release a poisonous fish at a mudflat in southeastern A ustralia 1,2 Ivan Sazima Museu de Zoologia, Universidade Estadual de Campinas, Campinas, SP, Brazil. Corresponding author: firstname.lastname@example.org Received on 26 March 2019. Accepted on 13 May 2019. ABSTRACT: Several waterbird species prey on fishes, and usually use only one sensory mode to detect this prey: herons hunt visually guided, whereas ibises mostly search tactilely guided. I report herein events in which a heron and an ibis caught and released a poisonous fish at a mudflat in southeastern Australia. A Great Egret (Ar dea alba) that targeted small gerreid fishes caught and immediately released the very toxic pufferfish Tetractenos hamiltoni, with bill washing and discomfort movements afterwards. Two Australian White Ibises (Threskiornis molucca) t hat probed for bottom-dwelling fishes and crabs caught and handled these pufferfishes for about 60 s, before releasing them. Next, the birds dipped the bill in the water and resumed hunting. Pufferfishes are rarely preyed on by birds, but an Australian bird that feeds on this fish type is the Silver Gull (Chroicocephalus novaehollandiae), which eats the pufferfish Torquigener pleurogramma when it is nontoxic or less harmful. KEY-WORDS: Ardea alba, fishing, prey handling, Tetractenos hamiltoni, Threskiornis molucca. Several waterbird species habitually prey on fishes, and forage. As hunting episodes generally are fortuitous and mostly use only one sensory mode to detect this prey brief, the three events were opportunistically observed type. For instance, herons and cormorants hunt their with bare eye or through a 70–300 mm telephoto lens prey guided visually, whereas ibises and spoonbills usually mounted on a SLR camera from a distance of about 3–8 search for their prey guided tactilely (Kushlan 1976 & m. Throughout the observational sessions, I used t he ad 1977, Recher et al. 1983, Swennen & Yu 2004 & 2008, libitum and sequence samplings (Altmann 1974), which White et al. 2007, Heath et al. 2009, Murray & Shaw are adequate to record fortuitous or rare events. Voucher 2009). Fish species hunted by herons and ibises vary digital photographs are on file at the Museu de Zoologia greatly, but pufferfishes are an uncommon prey of fish- da Universidade Estadual de Campinas (ZUEC). eating birds (Wodzinsky & Moreland 1966, Recher & On 11 January 2019 at mid-morning, I observed Recher 1968), likely due to powerful toxins secreted a Great Egret (Ardea alba) precisely and successfully by most pufferfish species and t heir ability to inflate striking at juvenile gerreid fishes called Common the body (Whitley 1953, Burklew & Morton 1971, Silverbiddy (Gerres subfasciatus) in the receding tide, Wainwright & Turingan 1997, Isbister et al. 2002, when it caught and immediately released a poisonous Oliveira et al. 2003). I report herein three episodes of a pufferfish locally named Common Toadfish (Tetractenos very poisonous pufferfish caught and released by a heron hamiltoni). Afterwards, the heron washed the bill twice and an ibis species at a mudflat (tide-influenced marsh) in (Fig. 1A) and displayed repeated signs of discomfort: it southeastern Australia. opened and closed the bill, and shook the head. After I observed the three catch and release events at about 2–3 min, the egret resumed hunting at the same o o the mudflat (33 50'18''S; 151 04'47''E; 2 m a.s.l.) of place. The pufferfishes are very common at the study site, the Waterbird Refuge wetlands at the Sydney Olympic where they move and forage solitarily or in groups of up Park in the urban area of Sydney, New South Wales, to about 20–30 individuals and often approach or join southeastern Australia. At the observation site the the Silverbiddy groups (Fig. 1B). mudflat is connected to the Parramatta River estuary and On 08 February 2019 at late morning, I observed is influenced by the tidal regime of the river. Besides the an Australian White Ibis (Threskiornis molucca) walking heron and the ibis, other diurnal fish-eating waterbir d slowly, probing in the then murky water and preying species (three herons, three cormorants, one spoonbill, on bottom-dwelling fishes and crabs, when it caught and one gull) used the site or closely adjacent areas to a Common Toadfish (Fig. 2A). The bir d handled the Revista Brasileira de Ornitologia 27(2): 2019 Waterbirds catch and release a poisonous fish Sazima Figure 1. While targeting juvenile Common Silverbiddy (Gerres subfasciatus) as prey, a Great Egret (Ardea alba) washes bill after it caught and immediately released a pufferfish (Tetractenos hamiltoni) in the receding tidal current (A). A group of juvenile Common Silverbiddy moves against the receding tide, the pufferfish T. hamiltoni (outermost spotted fish at right) joining the group (B). Figure 2. An Australian White Ibis (Threskiornis molucca) holds a pufferfish (Tetractenos hamiltoni) it caught while probing in muddy water (A). The ibis releases the pufferfish after handling it for about 60 s (B). pufferfish for about 60 s, and from time to time it made the studied wetlands, and I think that this assumption 2–3 lateral movements with its bill in the water before may be extended to other heron species, the spoonbill, releasing the fish (Fig. 2B). After the pufferfish re lease, and the gull as well. The observed Great Egret individual hunted the Common Silverbiddy juveniles with precise the bird dipped the bill in the water once and resumed visually-oriented strikes, and it likely caught the pufferfish hunting. On 18 November 2018 near midday I observed another ibis that caught and released a toadfish, but I by mistake: an individual of the latter could have had no the same advantageous view as in the description intercepted the heron's strikes at the targeted prey, as the above. However, I noticed that after catching the two fish species sometimes mingle (present study). The immediate release of the pufferfish and t he ensuing bill pufferfish t he ibis handled it for about 60 s and appeared washing plus the discomfort movements of the egret may to “cleanse” the fish t horoughly with lateral movements of the bill in the water. After this handling the bird released be related to the fact that several chemical compounds the pufferfish, dipped the bill in the water and resumed are aversive to birds and the avoidance reaction occurs hunting. at the first contact (Clark et al. 2014). On the other hand, the observed ibises were hunting with tactile- The three episodes reported herein indicate that the oriented shallow probing (sensu Kushlan 1977) in murky pufferfish T. hamiltoni is an unsuitable and potentially dangerous prey for at least a heron and an ibis species at water and they caught the pufferfishes possibly without Revista Brasileira de Ornitologia 27(2): 2019 Waterbirds catch and release a poisonous fish Sazima recognizing them immediately as an unpalatable and REFERENCES potentially dangerous prey. A possible explanation for the Altmann J. 1974. Observational study of behavior: sampling methods. birds handling the fishes for a while before releasing them Behaviour 49: 227–267. would be that the ibis is less sensitive than the heron to Birkhead T. 2013. Bird senses. London: Bloomsbury Publishing. the pufferfish poisonous secretion, or that its gustatory Burklew M.A. & Morton R.A. 1971. 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Toxicity of puffer fish - two species I have observed that T. hamiltoni discarded by fishermen (Lagocephalus laevigatus, linaeus [sic] 1766 and Sphoeroides spengleri, Bloch 1785) from the southeastern Brazilian coast. on jetties near the study site were not eaten by any Silver Journal of Venomous Animals and Toxins including Tropical Diseases Gull from groups of 5–20 individuals that lingered there 9: 1–10. waiting for a morsel such as fish offal or a discar ded catch. Recher H.F., Holmes R.T., Davis-Jr. W.E. & Morton S. 1983. Foraging A few birds inspected the pufferfishes, pecked at them behavior of Australian herons. Colonial Waterbirds 6: 1–10. Recher H.F. & Recher J.A. 1968. Comments on the escape of prey or pinched them once and lost interest on this potential from avian predators. Ecology 49: 560–562. food afterwards. These observations lend support to my Swennen C. & Yu Y. 2004. 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Sazima, Cristina Sazima, and Már cia Bianchi Zealand gannets. Notornis 13: 98–99. dos Santos for all the help during our stay in Sydney; Associate Editor: Cristiano S. Azevedo. Dione Serripieri for obtaining hard-to-find literature. Revista Brasileira de Ornitologia 27(2): 2019
Ornithology Research – Springer Journals
Published: Jun 1, 2019
Keywords: Ardea alba; fishing; prey handling; Tetractenos hamiltoni; Threskiornis molucca
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