OPINIONS: The Gemara states that a Nesher has all four signs of a Tamei (non-Kosher) bird. It does not have an extra toe (Etzba Yeseirah), it does not have a crop (Zefek), its gizzard cannot be peeled off (Kurkevano Niklaf), and it is Dores and eats.
What exactly is a Nesher? (It is important to note that the Sichas Chulin concludes his discussion of the Nesher by citing a number of early authorities who write that the exact identity of the birds mentioned in the Torah have become unclear and difficult for us to discern, "b'Avonoseinu ha'Rabim.")
(The following discussion is adapted from the forthcoming work, "The Torah Encyclopedia of the Animal Kingdom.")
(a) The Nesher is commonly understood to be the eagle. The CHIZKUNI (Vayikra 11:13), SEFER HA'ITUR, and YALKUT ME'AM LO'EZ also define the Nesher as the eagle ("eagila," "eagula," and "eagla" respectively).
TOSFOS (63a, DH Netz) says that it is a mistake to translate "Nesher" as "eagle," and that it must be some other type of bird. The Gemara here says that a Nesher has none of the signs of a Kosher bird, but we know that an eagle has an Etzba Yeseirah. The CHIDUSHEI HA'RAN here adds that according to both opinions of what the Etzba Yeseirah is (see Insights to Chulin 59:3) -- an additional toe at the back of the foot (RASHI), or a front toe that is larger than the others (RAN) -- an eagle has an Etzba Yeseirah.
(b) The RAMBAN and RAN write that the Nesher is the "Nesher ha'Kere'ach," the "bald Nesher," whose front toes are all the same size (and thus it does not have an Etzba Yeseirah, at least according to the Ran's definition of an Etzba Yeseirah). They cite support for this from the verse, "Expand your baldness like a Nesher" (Michah 1:16), implying that a Nesher is bald.
The Ramban and Ran are not referring to the bird known as the bald eagle, since that bird is not indigenous to Eretz Yisrael (but only to America). Also, it is not actually bald (it merely has white feathers on its head, and its name comes from the Old English word "balde," which means "white"). What bird, then, is the "bald Nesher"?
There is another bird that fits the descriptions of the Nesher in the verses and in the Gemara. RAV SA'ADYAH GA'ON and the IBN EZRA (Vayikra 11:13) translate "Nesher" into the Arabic term "Nesr," which refers to the griffon vulture.
While the griffon vulture is not entirely bald, as it has a white downy covering on its head and neck, it has no feathers on its head and thus it probably qualifies as being bald. There are other types of vultures that indeed are entirely bald. This feature relates to their habit of feeding on carrion. Vultures insert their heads into the carcasses of large animals in order to eat. Were their heads to be feathered, these feathers would become filled with blood and flesh of their prey, which would provide a place for dangerous bacteria to develop. By not creating it with feathers in its head and neck, Hash-m made the vulture able to safely insert its head and neck into the carcass without incurring this danger (SICHAS CHULIN, page 422).
While eagles were not so prominent in Eretz Yisrael, vultures formerly were very common and were the most magnificent birds of prey in the area (today, however, they are almost extinct, although they are being reintroduced into the wild by a number of vulture reserves). Moreover, there are a number of verses that describe characteristics of the Nesher that match the characteristics of the vulture, but not of the eagle. The verse describes the vulture as a bird that eats carcasses: "Does the Nesher rise up at your command, and make its nest on high? It dwells and abides on the rock, upon the crag of the rock, and the strong place. From there it seeks the prey, and its eyes behold from far away. Its young ones gulp blood; and where there are carcasses, there it is" (Job 39:27-30). Similarly, the verse says, "The eye that mocks his father, and scorns obeying his mother, will be picked out by the ravens of the valley, and the young Nesher will eat it" (Mishlei 30:17). Eagles generally do not feed on carrion, but rather they usually take live prey which they kill themselves. Vultures, on the other hand, are renowned for feeding on carrion; indeed, the griffon vulture eats nothing else.
Further evidence that the Nesher is the vulture and not the eagle is that it is described as being the highest flying bird. The verse says, "The pride of your heart has deceived you, you who dwell in the clefts of the rock, whose habitation is high; who said in his heart, 'Who shall bring me down to the ground!' Though you soar aloft like the Nesher, and though you set your nest among the stars, from there I shall bring you down, says Hash-m" (Obadiah 1:3-4). The IBN EZRA (Shemos 19:4), METZUDAS DAVID, and MALBIM (Iyov 39:27) write that the Nesher is the highest flying bird. While many birds reach high altitudes when migrating, the vulture is the only bird to reach high altitudes in its daily routine. In the course of normal activities, most birds fly below 500 feet, with no reason to expend energy in flying higher. Vultures, however, rise to great heights, sometimes over 10,000 feet. One reason for this is in order to scan larger areas for food. A second reason, which is cause for them to fly even higher, is to watch for other vultures heading towards a carcass. (The highest altitude recorded for any bird was in 1973, when a Ruppell's griffon vulture collided with a commercial airline over western Africa at an astonishing height of 37,000 feet).
The Nesher is referred to as the king of the birds, as the Gemara in Chagigah (13b) says. (See also Midrash Shemos Rabah 23:13, Shir ha'Shirim Rabah 3:23, and Koheles Rabah 2:29.) This may relate to the height at which it flies, and to its size -- the vulture has a wingspan that can measure eight feet, and is majestic as it soars. While the eagle is recognized today as a symbol of royalty, in ancient days it was the vulture that symbolized royalty. The griffon vulture was the symbol of royalty in ancient Egypt and Mesopotamia. Many the ancient cultures recognized the vulture as the ultimate king, and they worshipped a vulture-god. Assyrians and Persians depicted images of the griffon vulture, not the eagle, on their battle standards. (It was only in the time of Alexander the Great that the eagle was substituted as a symbol of royalty, due to the greater familiarity that Europe had with the eagle.)
While today, in the West, the vulture is commonly regarded as a loathsome creature, its natural characteristics are far from loathsome. The Torah presents it as an example of a loving and caring parent: "As a Nesher stirs up its nest, flutters over its young, spreads out its wings, takes them, bears them on its pinions -- so did Hash-m guide them, and there was no strange god with them" (Devarim 32:11-12). We find that vultures are particularly gentle parents. Female griffon vultures usually lay one egg, which both parents then incubate for an unusually long period of time (about seven weeks) until it hatches. The young are slow to develop and do not leave the nest until three or four months of age. This powerful devotion to their young entitles the vulture to be a symbol for Hash-m's love for the Jewish people.
(While most evidence indicates that the Nesher is the vulture, there is one statement in the Gemara that implies that it is the eagle. The Gemara (Sanhedrin 12a, Pesachim 87b) says that the Nesher alludes to Rome, whose symbol was the eagle. However, this difficulty on identifying the Nesher as the vulture can be reconciled. It is interesting to note that RAV DAVID TZVI HOFFMAN zt'l (cited by Torah Sheleimah, Parshas Shemini) says that the word "Nesher" includes both vultures and eagles. He reasons that eagles presumably need to be included somewhere in the list of non-Kosher birds. If they are not included in any of the other types, then they must be included in the category of Nesher.)
However, the Gemara here says that a Nesher has none of the four signs of a Kosher bird. Is this statement true with regard to a vulture?
1. Does a vulture lack an Etzba Yeseirah? According to Rashi, who defines an Etzba Yeseirah as a fourth toe at the back of the foot, a vulture has such a toe (indeed, all birds of prey have such toes, for it enables them to grasp their prey). Rabbi N. Slifkin suggests that perhaps the hallux (back toe) is rated as an extra toe only when it is comparable in length to the other toes. In vultures, the hallux is far shorter than the outer front toes, and vastly shorter than the middle toe. (The Sichas Chulin cites the PRI MEGADIM (Mishbetzos Zahav 82:3) who says that there are different types of Nesher, and perhaps one does not have such an extra toe. However, all of the known birds of prey have such a toe, and unless the Pri Megadim's intention is to say, as the SEFER YERE'IM (#68) writes, that perhaps the features of the Nesher have changed since the time of the Gemara, his explanation is difficult to understand. The ARUCH HA'SHULCHAN (YD 82:3) says that according to Rashi the back toe must be higher than the front toes in order to qualify as an Etzba Yeseirah, while the hallux of the vulture is on the same level as the front toes. This explanation also needs further elucidation, because the Etzba Yeseirah of a dove (a Kosher bird) is also on the same level as the front toes.)
The Ran, who defines Nesher as the vulture, and who defines Etzba Yeseirah as a larger front toe, asserts that the vulture does not have an Etzba Yeseirah, as all of its front toes are relatively equal in size. (The middle toe actually is larger. Rav Levinger suggests in MAZON KASHER MIN HA'CHAI that perhaps it is not as large as the same toe on other birds of prey and thus does not qualify as an Etzba Yeseirah, but this certainly does not seem to be the case. See www.zootorah.com/essays/vulture.htm for a photograph of the foot of a vulture, and for an in-depth analysis of the identity of the Nesher.)
2. Does a vulture lack a crop (Zefek)? Anatomically, the griffon vulture possesses a crop; its distended crop and gizzard can hold over thirteen pounds of meat at a time. (The only bird of prey that lacks any form of crop is the bearded vulture, but it is not bald and is therefore not a likely candidate for the Nesher.) However, the Halachic definition of a crop may differ from the zoological definition of a crop. The YAM SHEL SHLOMO (#115) points out that the crop must be of standard appearance. The hawk, for example, possesses a crop according to the zoological definition, but its shape is very different from the shape of a pigeon's crop, and the RAMBAN states that it therefore is not rated as a crop by the Gemara. The vulture's crop is similar to that of a hawk and likewise is not rated as a crop (see diagram at www.zootorah.com/essays/vulture.htm).
In addition, the definition of a crop may also relate to its function. Normally, a crop is used to soften the food (usually grain) that a bird eats. The crop of a vulture, in contrast, functions merely to store excess food. In fact, in a Kosher bird, the food goes first to the crop and then to the gizzard, while in a vulture, the food goes first to the gizzard, and the excess food then goes to the crop. The Sichas Chulin proposes that this is what the Gemara means when it says that the Nesher lacks a crop. He suggests that this is the intention of the ME'IRI who writes, "Some birds have a pocket in the place where a crop is usually situated, but it is not a crop."
3. Can a vulture's gizzard be peeled off (Kurkevano Niklaf)? A vulture certainly does not have this sign of a Kosher bird, as its gizzard cannot be peeled. The gizzard in most diurnal birds of prey is relatively thin-walled and saclike due to the soft nature of fish and meat (whereas birds that eat nuts and other hard, sharp foods, have gizzards with thick walls that can be peeled).
4. Is a vulture "Dores" when it eats? According to Rashi's first definition of Dores (that a bird holds its food in its claws and lifts what it eats to its mouth; see Insights to Chulin 59:2), a vulture is not Dores. However, Rashi also explains Dores to mean that the bird uses its claws to pin its food to the ground while it bends down to eat it, which the vulture indeed does.
According to those who explain that Dores means that the bird kills with its claws, and to those who explain that it means that it eats live prey without killing it, neither of these apply to the griffon vulture. Vultures generally feed only on carrion and never kill an animal (except in times of great need, when they may kill a small animal).


OPINIONS: The Gemara says that twenty of the twenty-four non-Kosher birds have three of the four signs of a Kosher bird. The only non-Kosher bird that has the fourth sign of a Kosher bird (and not the other signs) is either the Peres or the Ozniyah, which have no other signs of Kashrus besides that one sign.
TOSFOS (61a, DH Kol) points out that if we could determine which sign is missing from the twenty birds, then we would be able to easily determine whether any bird is Kosher or not. If a bird possesses that one sign and it is known not to be a Peres or Ozniyah, or it has any other sign of Kashrus (thus proving that it is not a Peres or Ozniyah), then we may assume that it is Kosher.
What is that missing sign of Kashrus?
(a) TOSFOS (62b, DH Mai) points out that RASHI and RABEINU CHANANEL understand that the fourth sign is "Kurkevano Niklaf," its gizzard can be peeled.
(b) TOSFOS himself considers the possibility that the fourth sign may be that it possesses a Zefek (crop).