Revista Cienfica, FCV-LUZ / Vol. XXXV Recibido: 08/07/2025 Aceptado:11/10/2025 Publicado: 04/11/2025 UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico 1 of 7 Revista Cienfica, FCV-LUZ / Vol. XXXV https://doi.org/10.52973/rcfcv-e35745 UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico Macroscopic and microscopic study of the brain structure of the common kestrel (Falco nnunculus) Estudio macroscópico y microscópico de la estructura cerebral del cernícalo común (Falco nnunculus) Burhan Toprak 1* , Aylin Bilen Çoban. 2 , Bahadır KilinÇ 3 1Yozgat Bozok University, Faculty of Veterinary Medicine, Department of Anatomy, Yozgat-TÜRKİYE 2Yozgat Bozok University, Faculty of Veterinary Medicine, Department of Histology and Embryology, Yozgat-TÜRKİYE 3Veterinary Control Central Research Instute, Pathology Laboratory, Ankara-TÜRKİYE *Correspondence author: burhan.toprak@bozok.edu.tr ABSTRACT This study was conducted to examine the macroscopic and light microscopic structures of the brain in kestrels (Falco nnunculus). In the study, brains from three adult kestrels that were brought in for treatment but could not be rescued, one from Keçiören Municipality Veterinary Affairs Directorate and two from Afyon Kocatepe University Wildlife Rescue and Rehabilitaon Centerwere used. The brains were properly removed and subjected to macroscopic and light microscopic examinaon procedures. The average brain weight was measured as 3.23 g, total length as 22.5 mm, and total width as 23.5 mm. The cerebrum, cerebellum, lobus opcus, and medulla oblongata were the prominent regions of the brain. A well-developed lobus opcus was observed, and small and rudimentary bulbus olfactorius structures were present on both sides of the midline at the rostroventral part of the cerebral hemispheres. In the cerebellum, transverse protrusions called folia cerebelli, varying in number between 9 and 10, and the fissura cerebelli separang them were seen. On the sides of the cerebellum and behind the lobus opcus, auricula cerebelli were idenfied. At the caudal part of the brain, the pons and medulla oblongata were present and separated by a slightly prominent transverse groove. In the light microscopic examinaon, small neurons located beneath the piamater in the cerebral cortex and irregularly distributed glial cells among them were observed. In the deeper corcal regions, large neurons with vesicular nuclei were idenfied. In the cerebellum, a typical three-layered structure consisng of molecular, Purkinjecell, and granular layers was present. In addion, numerous mulpolar neurons and supporng glial cells were found in the medulla oblongata, and ependymal cells were idenfied in the fourth ventricle. In the opc lobe, medium-sized spherical neurons containing few glial cells aracted aenon. With this study, the macroscopic and light microscopic structures of the brain in kestrels were revealed. The data obtained were compared with the morphological structures of the brains of other avian species, and similaries and differences were discussed.The findings are expected to contribute to the literature on the morphological characteriscs of raptors and serve as a foundaon for comparave anatomical and histological studies on wild bird species. Key words: Brain; common kestrel; Falco nnunculus; light microscopy; macroscopy RESUMEN Este estudio se realizó con el objevo de invesgar las estructuras macroscópicas y microscópicas del encéfalo en cernícalos vulgares (Falco nnunculus). Se ulizaron los encéfalos de tres ejemplares adultos de cernícalo que no pudieron ser recuperados tras recibir tratamiento, uno procedente de la Dirección de Servicios Veterinarios del Municipio de Keçiören y dos del Centro de Rescate y Rehabilitación de Vida Silvestre de la Universidad Afyon Kocatepe. Los encéfalos fueron extraídos conforme a los protocolos anatómicos y somedos a procedimientos de examen macroscópico y microscópico ópco. El peso cerebral medio fue de 3,23 g, con una longitud total de 22,5 mm y un ancho total de 23,5 mm. Las regiones destacadas del encéfalo incluyeron el cerebro y cerebelo, los lóbulos ópcos y la médula oblongada. Se observó un lóbulo ópco bien desarrollado, y en la parte rostroventral de los hemisferios cerebrales, a ambos lados de la línea media, se encontraron bulbos olfatorios pequeños y rudimentarios. En el cerebelo se idenficaron prominencias transversales denominadas folia cerebelli (en número de 9 a 10), separadas entre sí por fisuras cerebelosas. A los lados del cerebelo y detrás de los lóbulos ópcos se localizaron las auricular cerebelli. En la parte caudal del encéfalo se observaron el puente (protuberancia) y la médula oblongada, separadas por un surco transversal ligeramente pronunciado. En el examen microscópico ópco, se idenficaron pequeñas neuronas localizadas bajo la piamadre en la corteza cerebral, con células gliales distribuidas irregularmente entre ellas; en regiones corcales más profundas, se observaron neuronas grandes con núcleos vesiculosos. El cerebelo presentaba la estructura pica de tres capas: molecular, de células de Purkinje y granulosa. Además, en la médula oblongada se idenficaron numerosas neuronas mulpolares y células gliales de soporte, así como células ependimarias en el cuarto ventrículo. En el lóbulo ópco, destacaron neuronas esféricas de tamaño mediano con escasa presencia de glía. Con este estudio se documentaron las caracteríscas macroscópicas y microscópicas del encéfalo en el cernícalo vulgar, y se compararon los datos obtenidos con la morfología cerebral de otras especies de aves, discuendo semejanzas y diferencias. Se espera que los resultados contribuyan a la bibliograa sobre las caracteríscas morfológicas de las aves rapaces y sirvan de base para estudios comparavos anatómicos e histológicos sobre especies de aves silvestres. Palabras clave: Encéfalo; mernícalo vulgar; Falco nnunculus; microscopía ópca; macroscopía

Revista Cienfica, FCV-LUZ / Vol. XXXV UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico INTRODUCTION The common kestrel (Falco nnunculus) is a bird of prey belonging to the Falconidae family within the order Falconiformes. The primary food sources of common kestrels are small mammals, parcularly field voles and mice. Somemes they feed on amphibians, reples and other birds. They can also be seen hunng small mammals and insects, especially beetles and grasshoppers, on foot [1]. The avian brain is divided into three parts, like in mammals: the prosencephalon (telencephalon, diencephalon), mesencephalon and rhombencephalon (metencephalon, myelencephalon) [2]. In the avian brain, the rostral telencephalon consists of the cerebrum, thalamus and hypothalamus; the caudal diencephalon consists of the opc vessels. The mesencephalon is where the lobus opcus is located. The rhombencephalon consists of two parts, the rostral part of the metencephalon, which forms the cerebellum, and the caudal part of the myelencephalon, which forms the medulla oblongata [3 ,[4]. The brain is relavely large in birds. The cerebral hemispheres, opc lobes and cerebellum are well developed, while olfactory regions such as the olfactory bulb and hippocampus are relavely small [5]. One of the most characterisc structures of the bird brain is the opc lobe pair. The opc lobes, called occipital lobes in mammals, form the roof of the mesencephalon and are large, symmetrically located structures [6]. When the macroscopic organizaon of the avian brain was examined, it was reported that the hemispherium cerebri were separated from each other by a prominent fissura interhemispherica and small bulbus olfactorius structures were found ventrally. At the microscopic level, it has been stated that the cerebral cortex consists of six layers in the classical sense [7 ,[8]. In various avian species, the surface of the cerebral hemispheres is generally smooth and without prominent gyrus or sulci formaons as in mammals [3 , 9 , 10 , 11]. The cerebellum is a central organ for balance and movement funcons. Because of these funcons, they are larger and more organized than other parts in birds. The arbor vitae appearance observed in mammals is similarly present in birds. As in mammals, the cerebellum of birds also consists of two disnguishable layers: gray maer and white maer [12]. The gray maer consists of three layers: the molecular layer, the Purkinje cell layer and the granular layer [12 ,[13]. This study to reveal the macroscopic and light microscopic structural features of the brain of the common kestrel, a diurnal bird of prey. MATERIALS AND METHODS Sample collecon In this study, the materials consisted of brains from three adult common kestrels. Three adult common kestrels that had been brought for treatment to the Keçiören Municipality Veterinary Affairs Directorate (1 common kestrel) and the Wildlife Rescue and Rehabilitaon Center of Afyon Kocatepe University (2 common kestrels), but could not be saved, were used in the study. Permission to conduct the study on the common kestrels used in the research was obtained from the General Directorate of Nature Conservaon and Naonal Parks of the Ministry of Agriculture and Forestry under the official document number E-21264211-288.04-10698031. The brains were duly removed from the dead animals. The brains were fixed in 10 % formaldehyde soluon for easier dissecon and morphologic examinaon. The samples were then subjected to macroscopic and light microscopic examinaon procedures. Macroscopic examinaon The brain ssue of the common kestrel was examined anatomically in dorsal, ventral, lateral views and sagial secons. Measurements were taken from the brain, cerebellum and opc lobes with a digital caliper (Carbon Fiber Composites, Made in China). Aſter macroscopic examinaon, the brains were photographed using a digital camera (Canon Inc., IXUS 75, Made in Japan). Nomina Anatomica Avium [14] was used for the anatomical terminology in this study. Light microscopic examinaon The brain samples were fixed in a 10 % formaldehyde soluon. The enre brain ssue was trimmed to obtain sagial secons. For light microscopic examinaons (Leica DM 2500 LED, Leica 170 HD, Manufactured in Singapore), the samples were processed in an automac ssue processor (Leica ASP 300S), including washing with alcohol and xylene series, dehydraon, paraffin infiltraon, and embedding. Secons with a thickness of 5 μm were obtained from the prepared paraffin blocks using a microtome (Shandon, Finesse, Made in UK) and placed onto slides. The prepared slides were incubated in an oven at 60 °C for 40 minutes. Subsequently, the slides were stained using the Hematoxylin-Eosin staining method with a fully automatic device (Shandon, Varistain Gemini, Made in USA). The prepared slides were examined under a light microscope equipped with an aachment (Leica DM 2500 LED, Leica 170 HD, Manufactured in Singapore). The necessary examinaons were performed, and microscopic images of the secons were captured. RESULTS AND DISCUSSION Macroscopy of the brain The macroscopic structure of the brain in the common kestrel was examined in detail. The average brain weight was measured as 3.23 g, the total brain length as 22.5 mm, and the total brain width as 23.5 mm. The cerebrum, cerebellum, lobus opcus, and medulla oblongata were the prominent regions observed in the brain. The cerebrum constuted more than half of the brain. A fissura interhemispherica was idenfied between the right and leſt hemispheres. In the caudal region, between the cerebrum and cerebellum, there was a groove called the fissura subhemispherica, known as the transverse fissure in mammals. The anatomical features of the brain were evaluated from different perspecves in dorsal, ventral, and lateral views, as well as in sagial secons. Dorsal view When the brain of the common kestrel was examined from the dorsal view, the right and leſt hemispheria were idenfied in 2 of 7

Structure of the brain in the common Kestrel / Toprak et al. UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico the rostral region, while the lobus opcus, cerebellum, auricula cerebelli, and medulla spinalis were observed in the caudal re- gion. A fissura interhemispherica was present between the two hemispheria, and a fissura subhemispherica was observed be- tween the hemispheria and the cerebellum. Both hemispheria were bean-shaped in appearance and they occupy the dorsolat- eral surface of the cranial cavity. The average length and width of the cerebrum were measured as 15.5 mm and 11.75 mm, respecvely. In the cerebrum, eminena sagialis structures were idenfied in the rostromedial region, and valleculae were observed in the rostrolateral parts. The lobus opcus structures were prominently observed, appearing quite large, located cau- dally to the cerebrum and laterally to the cerebellum. No gyri or sulci were present on the dorsal surfaces of the cerebrum and lobus opcus. The cerebellum was located caudal to the cerebrum and medial to the lobus opcus. The average length, width, and height of the cerebellum were determined to be 11.5 mm, 10 mm, and 10 mm, respecvely. Transverse protrusions called folia cerebelli, ranging in number from 9 to 10, were ob- served on the surface of the cerebellum, separated from one an- other by fissurae cerebelli. The auricula cerebelli was observed lateral to the cerebellum and caudal to the lobus opcus. The medulla spinalis was prominently observed caudal to the cere- bellum (FIG. 1). FIGURE 1. The dorsal view of the common kestrel brain. Ht: Hemispherium cerebri, Va: Vallecula, Es: Eminena sagialis, Fi: Fissura interhemispherica, Fs: Fissura subhemispherica, Lo: Lobus opcus, Cb: Cerebellum, FoC: Folia cerebelli, FiC: Fissura cerebelli, F: Auricula cerebelli, Ms: Medulla spinalis. Ventral view In the ventral examinaon of the common kestrel brain, bulbus olfactorius structures were present rostral to the cerebral hemispheres and on both sides of the midline. These structures were quite small and underdeveloped a difference with mammals that have these structures more developed. A longitudinal fissure was observed just behind these structures, located between the cerebral hemispheres. The tractus opcus, chiasma opcum and lobus opcus were located caudally. The lobus opcus was divided from the cerebrum, tractus opcus and pons by a sulcus. The average length and width of the lobus opcus was 10 mm and 5 mm, respecvely. There was pituitary gland in the median line caudal to the chiasm opcum and rostral to the pons. The pons and medulla oblongata were observed in the caudal part of the brain and was separated by a slightly prominent transverse groove. A longitudinally located fissura mediana ventralis was seen on the pons and medulla oblongata. On both sides of this fissure, swelling was observed on both the pons and medulla oblongata. It was determined that the fissura mediana ventralis was deeper on the medulla spinalis located behind (FIG. 2). FIGURE 2. The ventral view of the common kestrel brain. Ht: Hemispherium cerebri, Bo: Bulbus olfactorius, Fl: Fissura longitudinalis ventralis, To: Tractus opcus, Co: Chiasma opcum, Lo: Lobus opcus, G: Pituitary gland, P: Pons, Mo: Medulla oblongata, Arrowhead: Fissura mediana ventralis, Ms: Medulla spinalis. Lateral view In the evaluaon of the lateral view of the common kestrel brain, valleculae and sagial protrusions were observed on the surface of the cerebral hemispheres. The pars frontalis cerebri, pars parietalis cerebri, and pars occipitalis cerebri were the structures idenfied in the lateral view from rostral to caudal. The fissura subhemispherica was observed to extend ventrally, demarcang the boundary between the hemispheria and the cerebellum. Similarly, this structure was found to connue caudoventrally between the cerebellum and the lobus opcus. 3 of 7

Revista Cienfica, FCV-LUZ / Vol. XXXV UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico The rostral part of the cerebellum was observed to indent into the caudal aspect of each cerebral hemisphere, with its central poron elevated, and then descending as it connued toward the medulla spinalis.On the surface of the cerebellum, 9 to 10 folia cerebelli were observed, along with fissurae cerebelli located between them. The well-developed auricula cerebelli was prominently observed lateral to the cerebellum, caudal to the lobus opcus, and dorsal to the mesencephalon. The mesencephalon, pons, medulla oblongata, and medulla spinalis were the other parts of the brain visible from the lateral aspect (FIG. 3). FIGURE 3. The lateral view of the common kestrel brain. Pfr: Pars frontalis cerebri, Poc: Pars occipitalis cerebri, Va: Vallecula, Ppa: Pars parietalis cerebri, Lo: Lobus opcus, Cb: cerebellum, FoC: Folia cerebelli, FiC: Fissura cerebelli, F: Auricula cerebelli, Mb: Mesencephalon, P: Pons, M: Medulla oblongata, Ms: Medulla spinalis Sagial secon view In the sagial view of the common kestrel brain, the bulbus olfactorius structures were observed in the rostroventral parts of the brain. Further posteriorly, the diencephalon and mesencephalon were located. The pons and medulla oblongata were prominently observed ventral to the cerebellum. The medulla spinalis was idenfied caudal to the medulla oblongata. The ventriculus quartus was observed between the cerebellum and the pons and medulla oblongata. In the sagial secon of the cerebellum, gray and white maer were observed (FIG. 4). FIGURE 4. The sagial secon view of the common kestrel brain. Bo: Bulbus olfactorius, Ht: Hemispherium cerebri, T: Diencephalon, Co: Chiasma opcum, Fs: Fissura subhemispherica, Cb: Cerebellum, Mb: Mesencephalon, P: Pons, Mo: Medulla oblongata, Ms: Medulla spinalis, Ok başı: Ventriculus quartus Light microscopy In the light microscopic evaluaon of the common kestrel brain ssue, the piamater was observed adjacent to the surface of the cortex, enclosing the brain ssue. Immediately beneath this layer, numerous small neurons with round nuclei were observed, along with irregularly distributed glial cells among them. In the deeper corcal regions, large neurons with prominent nuclei and extensive cytoplasm were idenfied. The neurons were disnguished by their lightly stained cytoplasm and vesicular nuclear structure. Glial cells with dark-stained nuclei were densely observed around the neurons (FIG. 5). FIGURE 5. Microphotograph showing the cerebral cortex of the kestrel composed of pyramidal neurons (arrowheads) and irregularly distributed glial cells (arrows), along with the piamater (green arrows) observed on the corcal surface, H&E, Scale bars: A, 500 µm; B, 200 µm; C, 50 µm 4 of 7

Structure of the brain in the common Kestrel / Toprak et al. UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico Histological examinaon of the cerebellar ssue revealed that it consisted of two main layers: the substana grisea (gray maer) and the substana alba (white maer). Addionally, the piamater, one of the meningeal layers, was located external to the substana grisea. Histologically, the substana grisea was observed as the outer layer, while the substana alba formed the inner layer. The substana grisea was found to consist of three disnct layers arranged from the outermost to the innermost: the molecular layer composed of small neurons, the Purkinje cell layer characterized by prominent Purkinje cells, and the granular layer rich in granule cells. The Purkinje cell layer was observed to be located between the outer molecular layer and the inner granular layer, exhibing a single-row arrangement composed predominantly of flask- or pear-shaped Purkinje cells, along with a smaller number of round or oval-shaped cells (FIG. 6A–B). The dendric extensions of the Purkinje cells were observed to extend into the molecular layer (FIG. 6C). FIGURE 6. Microphotograph showing cortex and medullary regions of the cerebellum in Kestrel. GM: Grey maer, WM: White maer, ML: Molecular layer, GL: Granular layer, arrow heads: Piamater, arrows: Purkinje cell layer, green arrows: dendrit of purkinje cell; H&E, Scale bars: A, 500 µm; B, 100 µm; C, 50 µm In the common kestrel, numerous neurons in the medulla oblongata exhibited a mulpolar structure with prominent nuclei, and supporve glial cells were present among them (FIG. 7A). The ventriculus quartus was lined with ependymal cells (FIG. 7B). Histological examinaon revealed that the lobus opcus consisted of medium-sized spherical neurons surrounded by a small number of neuroglial cells (FIG. 7C). FIGURE 7. Microphotograph showing numerous mulpolar neurons (arrowheads) and supporng glial cells (arrows) in the medulla oblongata of the kestrel (A), Microphotograph showing ependymal cells in the fourth ventricle of the kestrel (B), Microphotograph showing the opc lobe of the kestrel composed of medium-sized neurons (arrows) and a few neuroglial cells (arrowheads) (C), H&E, Scale bars: A, B, 200 µm; C, 50 µm In this study, the structural characteriscs of the brain of the common kestrel (Falco nnunculus) were examined at both macroscopic and light microscopic levels. The findings revealed both similaries and disnct differences when compared with previous studies conducted on other bird species. Relave to body weight, the brain of birds is 5 to 20 mes larger than that of reples. Within the class Aves, relave brain weight is lowest in ostriches (Struthio camelus), chickens (Gallus gallus domescus), and pigeons (Columbidae), while it is highest in parrots (Psiaciformes) [15]. In a study conducted in sparrowhawks (Accipiter nisus), it was reported that the mean brain weight was 3 ± 0.2 g, the mean brain length was 24 ± 2 mm and the mean brain width was 19 ± 2 mm, which was different from the findings of the common kestrel brain in this study [16]. In the literature, it has been reported that the cerebrum exhibits varying morphological shapes in the dorsal view in different poultry species [7 , 17 , 18]. For example, the cerebrum has been described as triangular in the chickens [17], and obtuse triangular in the ostriches [18] and owls (Strigiformes) [7]. Unlike mammalsit was also reported that in chickens, ostriches and owls, the brain surface was smooth and without gyri and sulci [7 , 18 , 19], similar to the findings of the common kestrel brain in the present study. It has been reported that the cerebral cortex consists of six layers histologically; these layers are molecular layer, outer granular layer, outer pyramidal layer, inner pyramidal layer, inner granular layer and mulform layer, respecvely [8]. In the microscopic examinaons performed in this study, a large number of pyramidal cells were observed in all layers of the cerebral cortex and these cells were similar to the pyramidal cell morphology described in previous studies [3 , 20]. It is reported that the cerebellum in bird species is more developed, especially compared to reples, and has a large surface area thanks to the folds on its surface. This structural feature is directly related to the cerebellum’s tasks of monitoring, regulang and correcng the locomotor system [20]. 5 of 7

Revista Cienfica, FCV-LUZ / Vol. XXXV UNIVERSIDAD DEL ZULIA Serbiluz Sistema de Servicios Bibliotecarios y de Información Biblioteca Digital Repositorio Académico Consistent with the macroscopic features reported in previous studies, the cerebellum is quite prominent in the kestrel brain samples [21]. In histological examinaons in geese, as demonstrated in this study, it was reported that the cerebellum consists of two main layers, substana grisea (gray maer) and substana alba (white maer), and the gray maer is organized as molecular layer, Purkinje cell layer and granular layer. While the molecular layer contains a small number of small nerve cells, the granular layer has been found to contain a large number of granular cells and the dendrites of Purkinje cells extend into the molecular layer [22]. Similarly, in a study in pigeons, it was reported that the cerebellar cortex consists of three layers; the outermost molecular layer consists of small neurons and glia cells, the granular layer contains dense granular cells with dark nuclei, and Purkinje cells are located in a single row between these two layers [23]. The lobus opcus is an important brain structure responsible for processing visual percepon in birds, and its morphological characteriscs can vary depending on the species’ lifestyle, acvity me and migraon distance. Vincze et al. [24], reported that migraon distance has an effect on brain size and lobus opcus volume; the opc lobes of birds migrang long distances are larger. This has been aributed to the need for high-resoluon visual processing. As a maer of fact, in the common kestrel specimens examined in this study, similar to previous studies [25], it was observed that the opc lobe was large, prominent and located below the cerebrum. It has been suggested that diurnal bird species have a more advanced opc lobe structure due to their need for high vision and the capacity to process visual data [26]. This advanced opc lobe structure observed in the present study is consistent with the kestrel being a diurnally acve and predatory species. A study in the African ostrich (Struthio camelus camelus) reported that the opc lobe is composed of medium-sized neurons with few neuroglia, similar to the kestrel brain samples examined in this study [20]. The anatomical posion of the bulbus olfactorius varies significantly between species. In some species, this structure is located in front of the cerebral hemispheres and disnctly separate, while in others it is located very close together or on the undersurface of the hemispheres. In some species, the two bulbus olfactorius fuse completely in the midline to form a single structure [27]. In the kestrel brain samples examined in this study, the bulbus olfactorius structures were symmetrically located on the ventral side of the brain and were described as small and underdeveloped structures. Although this morphological feature suggests a limited reliance of the kestrel on its sense of smell during hunng, recent studies have shown that almost all bird species, regardless of the relave or absolute size of the bulbus olfactorius, are able to detect odors and that this ability is oſten directly linked to specific ecological funcons [28]. To beer understand the effect of bulbus olfactorius size on olfactory capacity, comparave studies across different bird species would be beneficial in supporng this relaonship. In studies conducted on pigeons and chicks, a thin membranous structure extending from the surface of the medulla oblongata to the subarachnoid space at the caudal end of the ventriculus quartus has been described. It was reported that this membrane is connuous with the ependymal cells and that there is no direct anatomical connecon with the subarachnoid space [29]. CONCLUSION This study has thoroughly examined the brain structure of the common kestrel (Falco nninculus), a diurnal bird of prey, at both macroscopic and light microscopic levels, revealing morphological characteriscs specific to this species. Macroscopic findings showed that the cerebrum consisted of two hemispheres with a flat surface, separated by a prominent fissura interhemispherica; the opc lobes were large and well developed, and the cerebellum was convoluted with numerous folia cerebelli. The presence of ny and underdeveloped bulbus olfactorius on the ventral side suggests that the visual system is more dominant than the olfactory system in this species. Microscopic examinaon revealed the presence of pyramidal neurons and dense glial cells in the cerebral cortex, while the typical three-layered structure of the cerebellum and the histological integrity of prominent Purkinje cells were observed. In addion, numerous mulpolar neurons and supporng glial cells were found in the medulla oblongata and the fourth ventricle was found to be covered with ependymal cells. These data show that the nervous system organizaon of the common kestrel has evolved in accordance with environmental condions and ecological requirements, and will contribute to comparave anatomical and neurohistological studies on the brain morphology of birds of prey. ACKNOWLEDGEMENT The authors would like to thank Keçiören Municipality Veterinary Affairs Directorate and Afyon Kocatepe University Wildlife Rescue Center for their contribuons to the supply of materials. 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