Re-Thinking Wing-Flashing in Mimidae, with New Reports from Paraguay

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Re-thinking wing-flashing in Mimidae, with new reports from Paraguay

Paul Smith & Sergio D. Ríos

To cite this article: Paul Smith & Sergio D. Ríos (2019): Re-thinking wing-flashing in Mimidae, with new reports from Paraguay, Ethology Ecology & Evolution, DOI: 10.1080/03949370.2019.1575911 To link to this article: https://doi.org/10.1080/03949370.2019.1575911

Published online: 29 Mar 2019.

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Re-thinking wing-flashing in Mimidae, with new reports from Paraguay

Wing-flashing is a frequently-cited behavior reported in multiple species of the genus Mimus sensu lato (Passeriformes Mimidae), including Grey catbird Dumetella carolinensis (Batts 1962; Michael 1970), Northern mockingbird M. polyglottus (Gander 1931; Sutton 1946; Tomkins 1950), Tropical mockingbird M. gilvus (Haverschmidt 1953; Whitaker 1957), Bahama mockingbird M. gundlachii (Aldridge 1984), Long- tailed mockingbird M. longicaudatus (Bowman & Carter 1971), Chalk-browed mockingbird M. saturninus (Halle 1948), Galapagos mockingbirds (Nesomimus spp.) (Hundley 1963; Bowman & Carter 1971; Burtt et al. 1994), Socorro mockingbird Mimodes graysoni (Curry & Martínez-González, pers. comm. in Burtt et al. 1994), and Brown thrasher Toxostoma rufum (Laskey in Sutton 1946; Tomkins 1950; Thomas in Whitaker 1957; Michael 1970). Though the behaviour is clearly widespread in the family it remains poorly described in most neotropical species (Burtt et al. 1994) and its function is still debated. Previous works have associated wing-flashing with defensive behaviour (Hicks 1955; Sazima 2015), wariness (Sutton 1946) foraging (Gander 1931; Allen 1947) and breeding activities (Dhondt & Kemink 2008). Wing- flashing as currently understood occurs in both sexes and even immature individuals (Horwich 1965). However there is much confusion as to what actually constitutes wing-flashing and a lack of clarity may well be adding to the misunderstanding (Hailman 1960). In this contribution we describe, illustrate and discuss observations of wing flashing in the two mockingbird species known to occur in Paraguay: Chalk-browed mockingbird Mimus saturninus and White-banded mockingbird Mimus triurus. Such behaviour is reported for the latter species for the first time. We also provide some additional comments on the contexts of the behaviour, the need for proper documentation of the observed behaviours and suggest some overlooked concepts that future researchers should bear in mind when developing their observation methodologies.

White-banded mockingbird Mimus triurus

An adult of this species was observed wing-flashing repeatedly at short intervals on a lawn at Laguna Capitán, Presidente Hayes Department, in the central Paraguayan Chaco on 10 April 2016 by P. Smith (and David Winterbottom) at around 3 pm. The wings were opened rapidly to their full extent in a single movement, held open parallel to the body for a few seconds and then subsequently closed again (Fig. 1). This species has distinctive broad white bands across the black-tipped wing and conspicuous white outer tail feathers that combine to form an eye-catching jizz in flight. The tail, however, remained closed at all times during wing-flashing. Short runs were made

Fig. 1. — White-banded mockingbird Mimus triurus wing-fanning at Laguna Capitán, Presidente Hayes department, Paraguay on 10 April 2016 (P. Smith). between flashes and though the bird was assumed to be foraging (from the way it was looking at the ground between runs) it was not observed to capture prey. The bird was observed from a distance of approximately 100 m on a large open lawn, with no visible threats or predators. The distance involved and the fact that the bird was initially facing away from the observers (and in fact the initial short runs were away from the observers) means that it is possible to rule out this being a defensive response to our presence. No evidence of breeding activity was noted. To our knowledge this is the first report of this behaviour in this species.

Chalk-browed mockingbird Mimus saturninus

Wing-flashing in this species was mentioned but not described by Halle (1948) based on observations in Argentina, and in more detail by Argel-de-Oliveira (1989)on the basis of extensive observations in São Paulo, Brazil. Three separate observations of different wing-flashing postures in this species were made: two by S.D. Ríos at Parque Guasú Metropolitano, Asunción, Central Department, and a third by P. Smith in Encarnación, Itapúa Department. The first observation (Fig. 2A–C) was made on 18 October 2014, when an individual responded to the presence of a passing Black tegu Salvator merianae lizard (Squamata Teiidae) by positioning itself close to the tail of the lizard and making short jumps into the air whilst lifting its wings above the horizontal and bringing them abruptly down in front of the head. The bird pursued the lizard for approximately 20 m until it disappeared into nearby vegetation. A pair of fledglings that had recently left the nest were present nearby. The bird was seen to touch the lizard with its bill and Forum 3

Fig. 2. — (A–C) Chalk-browed mockingbird Mimus saturninus wing-lifting in response to threat posed by aBlackteguSalvator merianae at Parque Guasú Metropolitano, Asunción, Central Department, Paraguay on 18 October 2014 (S. Ríos). (D) Chalk-browed mockingbird Mimus saturninus wing-fanning at Parque Guasú Metropolitano, Asunción, Central Department, Paraguay on 25 October 2014 (S. Ríos). feet during the observation, confirming that the role of wing-flashing in this case was defensive. The omnivorous Salvator merianae is a known predator of bird’s eggs and chicks (Mercolli & Yanosky 1994). A second observation of presumably the same group was made on 25 October 2014 at the same locality. This individual was foraging in low grass and held a small grasshopper (Orthoptera Acrididae) in its bill. It adopted a head-down posture with horizontal spread wings which were maintained open for a few seconds (Fig. 2D), before they were closed again and it changed place, repeating the action. A third observation of a different posture was made on 10 December 2018 in an urban area of the city of Encarnación. An adult bird was seen standing on a roadside sidewalk close to the city centre. At the approach of pedestrians from either side a bird first extended its wings slowly parallel to the body, before suddenly switching to the wing- up posture revealing the underwing which it held for about 1 sec. This same movement was repeated a second time before the bird flew away. Unfortunately it was not possible to obtain images of the bird performing these movements. Nor was it possible to observe any additional birds (neither adult nor young) before the interaction ended.

Comments on wing-flashing

Burtt et al. (1994) reported wing-flashing behaviour in Galapagos mockingbirds (Nesomimus spp.) noting the difference between the rapid, “smooth” wing-flashing of 4 Forum these species (with no white on their wings) and the “hitching” motion associated with the Northern mockingbird M. polyglottus which has conspicuous white wing patches. They suggested that wing-flashing evolved first and that the white patches were part of an evolution of “dramatic effect” and the evolution of conspicuous wing patches “would select for exaggerated wing-flashing, whether the behaviour functioned to signal conspecifics or startle prey” (Hailman 1960). The observation of “smooth” wing-flashing in Mimus triurus, perhaps the species with the most dramatic white wing patches in the entire family, would appear to contradict this theory, while Argel- de-Oliveira (1989) describes wing-flashing in up to five stages in Mimus saturninus which has hardly any white on the wing. However, this assumes that wing-flashing is a stylized behaviour and that it is a single behaviour with a single function, before overstepping the available data by assuming that the evolution of white on the wings is associated with wing-flashing at all. The observation reported here of breeding Mimus saturninus wing-flashing at Salvator merianae, a potential nest predator, is further confirmation that wing-flashing can have a defensive function during breeding as demonstrated by Dhondt and Kemink (2008). This supports an observation by Sazima (2015) who referred to wing-flashing amongst defensive techniques employed by a group of mockingbirds (two adults and three juveniles) in a tree under threat from the snake Philodryas olfersii (Squamata Dipsadidae). Sazima (2015) concluded that mobbing by birds in family groups fulfilled three functions “alerting others”, “move on hypothesis”, and “cultural transmission hypothesis” as detailed by Curio (1978). That such behaviour be linked to breeding (presence of chicks or nests) is entirely plausible (Dhondt & Kemink 2008)as it involves parent birds (well capable of simply flying away) defending vulnerable offspring, and as such may be analogous to the broken wing displays of certain plovers (Simmons 1951; Bergstrom 1988; Byrkjedal 1989) where adult birds are willing to risk harm or injury in order to protect offspring. The images included in Sazima (2015) shows a bird lifting its wings vertically similar to the birds under threat from Salvator merianae documented here, as do the birds illustrated by Sutton (1946) and Audubon (1840) (defending a nest under attack from a rattlesnake). Though Dhondt and Kemink (2008) do not thoroughly describe the postures they observed, their mention of birds moving “both wings simultaneously upward above their back” is also consistent with this posture. Halle (1948) also refers to wing “lifting or flashing” in Chalk-browed mockingbird M. saturninus in Argentina suggesting that he was also probably referring to this posture, though he does not provide a context. This posture is, however, quite different to the wing-open “umbrella” posture documented here for apparently foraging M. triurus and M. saturninus, and the horizontal wing movements of foraging birds mentioned by Wampole (1949), suggesting that different situations may elicit different wing- flashing responses, the functions of which may not necessarily be related. This incon- sistency in what wing-flashing actually is was recognized by Hailman (1960) who described some of the observed variations, but he subsequently failed to treat different postures as different behaviours in his analysis. Argel-de-Oliveira (1989) illustrates a Mimus saturninus adopting a wing-open “umbrella” posture in São Paulo, Brazil and provides a description of the contexts in which wing-flashing was observed. The author alludes to variations in the display, including events of “hitching”, but unfortunately does not attempt to link these variations to observed events. Wing-flashing is described as “most frequent” in birds foraging on the ground, but of 339 “wing-flashing” exhibitions in 90 foraging sequences, Forum 5 just 6.7% were immediately followed by a strike at the ground, and of 297 total strikes at the ground observed, wing-flashing preceded just 11.4% of them. This suggests not only limited employment but also limited success. Furthermore “wing-flashing” (type not clarified) was also observed by birds arriving and leaving at the nest (12 observations), standing on prominent perches (5 observations), in response to the close presence of observers (3 observations) and following installation of a hide close to the nest (1 observation). Hayslette (2003) was also unable to find a strong link between wing-flashing and foraging success in Northern mockingbird M. polyglottus, though again the precise posture being observed was not described. Both these studies contra- dicted the conclusions of Hailman (1960) who found foraging to be the principal factor involved in wing-flashing, though according to the same author young birds may perform it “irrelevantly” and it is “possibly” used in predator displays. The more complex display observed in the urban bird combined elements of both of these postures. Whilst it is tempting to suggest that the approaching pedestrians from both sides was associated with the behaviour, insufficient information is available on the context of this brief observation to draw any firm conclusions. Consequently, we propose that not only are the functions of wing-flashing likely to be multiple, but the behaviours classified as wing-flashing in the literature likely refer to multiple behaviours, involving distinct movements (smooth or “hitched”), diverse postures (which all involve opening the wings) and varying contexts. The failure to recognize this has contributed to confusion as to their interpretation by authors who may have automatically assumed that any open-wing display they observe is “wing-flashing” and has resulted in apparently contradictory conclusions. Wing-flashing behaviours may or may not have single explanations with single postures applicable to a single context, but our current understanding undoubtedly over- simplifies what is happening. Detailed description of the type of “wing-flashing” observed is key to interpreting the function of the behaviour being observed, and in its absence the application post hoc of theories to published observations is largely futile. We suggest that at least two different types of “wing-flashing” are reported here in the Paraguayan species and are possibly present throughout the family. One is defensive in which the wings are lifted vertically above the body and the tail is partially fanned and was colloquially referred to as “archangel fashion” by Dhondt and Kemink (2008). The second is of undetermined function and involves the wings being held out horizontally to the body for a brief period and the tail unfanned. This second posture may be associated with foraging (Hailman 1960; Hayslette 2003) but more investigation is required in order to confirm its purpose and to affirm or disprove a proposed link to breeding. For clarity we suggest the term “wing-lifting” for the former, defensive posture with wings raised vertically above the body in an erect posture and “wing- fanning” for the latter with spread wings held horizontally in an “umbrella” fashion, with both covered under the broader term “wing-flashing” as previously described in the literature. However, this distinction does not take into account the role of “hitching” and may itself also be an over-simplification of the complexity of wing-flashing, nor does it account for the combination of both observed in the urban bird in Encarnación. We urge careful documentation of future cases to help clarify these issues. The presence of wing-flashing in species that lack white in their wings that so confused Halle (1948) need not be so confusing in the context of the existence of multiple wing displays by mimids which do not require “startling” of prey or predators 6 Forum as a central explanation. In fact the two species that show most white on the wings, White-banded mockingbird Mimus triurus and Brown-backed mockingbird M. dorsalis both perform mate-attracting displays that involve displaying the dramatic wing and tail pattern, the former singing and performing short jumps from the ground, and the latter with a more aerial display in which the wings and tail are fanned (Fjeldså & Krabbe 1990). It would seem that such visual displays associated with finding a mate and hence directly impacting on reproductive success would be more likely to provide a strong selective force for the presence of eyecatching white wing patterns than occasional encounters with predators or the need to periodically startle insects in order to catch them. Given the noisy and sometimes aggressive behaviour that accompanies such encounters, it seems improbable that white wing patches are required to startle predators which may be many times the size of the birds themselves, especially given that this behaviour occurs successfully in species that lack bold wing patterns (Sazima 2015). In fact there are several other explanations worthy of investigation as to why wing-lifting might evolve in this defensive context including, making the individual appear much larger than it really is, creating a visual cue to accompany vocal cues in social birds in a stressful situation or simply positioning the wings in a manner that a sudden downward stroke can assist rapid escape should the predator choose to attack. Nor does wing-fanning require white wing patches in order to assist with foraging. The assumption that wing-fanning has the intention to “startle” prey into action needs to be examined in terms of movements, colours (including those beyond the visible spectrum) and patterns that are actually effective in startling insects from their hiding places. Certainly the movements observed in the foraging White-banded mockingbird Mimus triurus reported here did not seem consistent with attempts to startle prey, the wings being opened smoothly rather than suddenly, and being held open for several seconds before closing. A similar “umbrella” posture is also documented in Chalk-browed mockingbird M. saturninus, a species lacking a bold wing pattern, and further suggesting that wing pattern played only a minor role, if any at all, in the evolution of wing-fanning. Future studies need to carefully consider the possibility of multiple cryptic behaviours being masked by “wing-flashing”, recording details of the posture, movement, environmental conditions and context of observations. In addition to the oft- repeated defensive and foraging hypotheses, other hypotheses need to be re-examined, including the provision of shade for better vision in highly contrasting light conditions, some other kind of visual communication with other group members related to kin location, territorial signalling or perhaps even just simple stretching (Wampole 1949; Selander & Hunter 1960; Mueller & Mueller 1971; Argel-de-Oliveira 1989; Hayslette 2003). Furthermore the role of these behaviours across the family also needs to be quantified, including a more thorough taxonomic inventory and local inter- and intraspecific variations in employment and frequency. The role of multiple, reliable, well-documented, regional field observations in deciphering this kind of puzzle is vital and we encourage the publication of natural history notes reporting unusual behaviours, especially in the Neotropics where such information is rarely available. Where possible such behaviours should be illustrated as well as described to avoid misinterpretation and as much accompanying data as possible provided, regardless of its immediate applicability to the observation as understood by the observer. Forum 7

Acknowledgements

Both authors are grateful to the Pronii program of CONACYT Paraguay for its support. David Winterbottom accompanied P. Smith in the field for the Laguna Capitán observation.

Disclosure statement

No potential conflict of interest was reported by the authors.

Orcid

Paul Smith http://orcid.org/0000-0002-8758-4816

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PAUL SMITH Centro IDEAL, Para La Tierra, Mariscal Estigarribia 321 c/Tte, Capurro, Pilar, Dpto. Ñeembucú, Paraguay and FAUNA Paraguay, Carmen de Lara Castro 422, Encarnación, Dpto. Itapúa, Paraguay (E-mail: [email protected]).

SERGIO D. RÍOS Departamento de Arqueología y Paleontología, Secretaría Nacional de Cultura, Asunción, Paraguay and Museo Nacional de Historia Natural del Paraguay, San Lorenzo, Dpto. Central, Paraguay.