Morphological features of the tongue and laryngeal entrance in two predatory birds with similar feeding preferences: common kestrel (Falco tinnunculus) and Hume’s tawny owl (Strix butleri)

Abstract

The aim of this investigation was to describe the morphological characters of the tongue of two predatory birds with similar feeding preferences, i.e. the common kestrel and Hume's tawny owl. Descriptive information on the lingual morphology of these two birds, particularly Hume's tawny owl, is incomplete. We found that the lingual apex of the owl has an oval, concave, shovel-like form with a bifid lingual tip, while that of the kestrel has the shape of a horny tip-like spoon with a central process in addition to there being several filiform-like papillae on the dorsal surface of the apex and body. In the owl, the dorsal surface of the apex and body is subdivided into four U-shaped regions: lingual tip, two lateral regions and a median region. The two lateral regions are characterized by the presence of papillae and several openings of lingual glands, while the median region carries filiform-like papillae. In both birds, the papillary crest is located between the body and root. In the kestrel, there is an additional row of papillae rostral to crest, while in the owl there is a rostral lateral extension of papillae on the lateral lingual surface so the distribution pattern has a W-shape. In the kestrel, the posterior part of lingual body has several openings of glands, while the root lacks glands completely, although it has many taste buds. In the owl, the lingual root is folded and has a large number of gland openings. In the kestrel caudally to the glottis, there are two paramedian transverse rows of pharyngeal papillae with a pair of median huge papillae, while in the owl, there is only one transverse row of papillae. The dorsal and ventral lingual surfaces of both birds are lined with non-keratinized stratified squamous epithelium.

Surface ultrastructural descriptions of the oropharyngeal cavity of Anas querquedula

“…The current work found that the pharyngeal papillae take the diamond shape with numerous caudally directed mechanical conical papillae, while in the coot (Abumandour & El‐Bakary, ) reported that the pharyngeal papillae take a heart‐shaped appearance. The presence of the conical pharyngeal papillae described in the present study were reported in many avian species as noted by Abumandour (, ) and Abumandour and El‐Bakary (, )). However, there are some articles reported the presence of the two transverse rows of pharyngeal papillae (Abumandour, ).…”

“…The current study observed that the median longitudinal lingual sulcus extended along the dorsal surface of the lingual apex and body, in which it is deep in the rostral ⅔ of the tongue and shallow in the caudal ⅓ of the tongue on the lingual prominence, similar position of the groove reported in Eurasian coot (Abumandour & El‐Bakary, ), and common kestrel (Abumandour & El‐Bakary, ). While, the shallow median lingual sulcus located along the dorsal surface of the lingual body including the lingual prominence observed in the Northern pintail (El Bakary, ) and domestic duck (Skieresz‐Szewczyk & Jackowiak, ), while it is present only on the dorsal surface of the lingual body (Jackowiak et al, ) in the domestic goose, but it is present on the anterior region of the lingual body and absent in the lingual apex and prominence of the Middendorff's bean goose (Iwasaki et al, ), but present in the caudal part of the lingual body as noted in the house sparrow (Abumandour, ).…”

“…The lingual shape is species‐specific among avian species and related to the shape of the lower jaw, feeding styles, types of available food particles (Abumandour & El‐Bakary, , ; Jackowiak, Skieresz‐Szewczyk, Godynicki, Iwasaki, & Meyer, ). The shape of the bird's tongue contains two possibilities for adaptation to a lower beak; the first possibility, include that it is closely correlated with the lower beak as observed in the current work and by Abumandour (), Abumandour and El‐Bakary (, ), Emura, Okumura, and Chen (), and Parchami, Dehkordi, and Bahadoran (), but the second possibility, include that there is no relationship between the shape of the tongue and the size of the lower beak in which there is two conditions of the tongue, may be short tongue such as the hoopoe (Abumandour & Gewaily, ), the ratite birds (Jackowiak et al, ; Santos et al, ), and the white stork (Jackowiak et al, ) or may be the tongue longer than the lower jaw such as in the wood‐peckers bird (Emura, Okumura, & Chen, ).…”

“…The lingual apex is the most lingual part that indicate the environmental adaptation with the feeding behavior and the different types of foods available, as the lingual apex is adapted to perform different action in the feeding mechanism as the foods collection, food manipulation, and help in the direction of the foods toward the esophagus (Abumandour & El‐Bakary, ). This is clear in the current study on the migratory omnivorous Garganey ( A. querquedula ), as the most water birds has the round‐shaped lingual apex with an anterior spatula‐like structure (Jackowiak et al, ; Marzban Abbasabadi & Sayrafi, ; Skieresz‐Szewczyk & Jackowiak, ), but there is another water birds not contain the lingual nail as the Eurasian coot (Abumandour & El‐Bakary, ), however, the tongue of the nutcracker (one of the passerine birds) has a pair of dagger‐like processes that play an important role in the raising and ejection the seeds toward the median longitudinal lingual sulcus (Jackowiak et al, ).…”

“…The focused point for the most researchers is the studying the morphological appearance of the tongue and their adaptation with the different feeding styles (Abumandour & El‐Bakary, ; Al‐Ahmady Al‐Zahaby, ; Jackowiak, Andrzejewski, & Godynicki, ; Pasand, Tadjalli, & Mansouri, ). Recently, there are some morphological articles designed to study the morphological characterization of the oropharyngeal cavity (tongue, laryngeal mound, and the palate) and its adaptations with the feeding behavior and the available food materials (Abumandour, ; Abumandour & El‐Bakary, ; Abumandour & Gewaily, ; Kobayashi, Kumakura, Yoshimura, Inatomi, & Asami, ; Santos et al, ).…”