Folia Historico-Naturalia Musei Matraensis - A Mátra Múzeum Természetrajzi Közleményei 21. (1996)

of the Lesser Kestrel is relatively high, but the GW/GH values are within the range of the measurements of the Merlin, Kestrel and Red-footed Falcon (Plate V, Figure 1). The shape of the neurocranium, and especially its contour in lateral view is different in the examined species. In the Merlin the frontal part of os frontale is more protruding, but the nasal part is more concave, and hence the orbital part of the cranium is more flattened than in the Hobby. Consequently the cranium in lateral view is more elongated. In the Red-footed Falcon the frontal part of os frontale is less protruding than in the former two species, and in the Kestrel even less protruding. A similar phenomenon is found in the prominentia cerebellaris, which protrudes more (in caudal direction) in the Hobby and Merlin than in the Kestrel and the Red-footed Falcon. As a consequence of all these features the neurocranium of the Merlin is more cornered than that of the Hobby (Plate XXXIV, Figures 1-2). The neurocranium of the Kestrels is more rounded, especially that of the Kestrel's (Plate XXXIV, Figures 3-5). The ratio of the largest width of the cranium (GW) and the width of os squamosum measured at the alae tympanicae is different in the Falcon species. In the Hobby the former is always bigger than the latter, but in the other species the two measurements are usually equal, but in several cases the TW value is greater (see the GW/TW values). The processus supraorbitalis of os prefrontale (lacrimale) is wider in the Merlin than in the Hobby, it narrows down only near the apex. The arching of the two processus supraorbitales on the two sides is the widest in this species (Plate XXXIV, Figure 7). In the Hobby this bone is narrower, narrows down towards the apex gradually, and the arch of the bones in dorsal view is smaller (Plate XXXIV, Figure 6). In the Kestrel and the Red-footed Falcon the processus supraorbitalis is narrow, similar to the Hobby, but less arched. In lateral view in the Hobby the processus supraorbitalis is arching higher, than in the Merlin (Plate XXXIV, Figures 1-2). In the Lesser Kestrel the processus supraorbitalis is short and wide. In the Hobby and Merlin the os prefrontale at the faciès articularis frontonasalis is ossified to the cranium in most of the cases. In the Kestrels it happens very seldom, probably only in old specimens. It is not an absolutely reliable but usually quite good distinguishing feature that the caudo-lateral edge of the os palatinum in the Merlin and Red-footed Falcon is more pointed and angled than in the Hobby, Kestrel and Lesser Kestrel, where this edge is more rounded and arched (Plate XXXV, Figures 3-4). In the Hobby the plate of the os palatinum is longer, and consequently the processus premaxillaris is shorter than in the other species. One of the best identifying key between the species is the longitudinal rib on the palatal part of os premaxiUare, starting from the tip of the beak. This more pronounced in the Red-footed Falcon, where there is a protrusion (tip) at the middle of this rib. In the Hobby and Lesser Kestrel this rib is well developed, but the tip at the middle is missing. The rib is either straight or moderately rounded. In the Kestrel the rib is smaller, but still very visible, in lateral view its shape is a bit concave. This rib is smallest in the Merlin, that sometimes can not be seen at all (Plate XXXTV, Figures 1-5). The naiTowest measure of the cranium (MW) - which is found at the pars nasalis of os frontale - is different in the species, compared to the greatest length of the cranium (GL) the rank of the species is the following: F. subbuteo > F. vespertinus > F. tinnunculus > F. columbarius Above the eyes the cranium is the widest in the Hobby, and the narrowest in the Merlin. We get the same rank if we compare the MW value to the width of the cranium (GW/MW). The fossa temporalis is bigger in the Red-footed Falcon than in the other species (TW/FW value is the highest) (Plate XXXV, Figures 1-2). 18