Plumages, Molts, and Structure

The Eurasian Griffon has 10 functional primaries (numbered distally, from innermost p1 to outermost p10), usually 23–25 secondaries (numbered proximally, from innermost s1 to outermost s20–s22 and including three tertials numbered distally, from t1 to t3), and 12 rectrices (numbered distally on each side of the tail from innermost r1 to outermost r6). Accipitrine hawks (Acciptridae) are diastataxic (see 10 Bostwick, K. S., and M. J. Brady (2002). Phylogenetic analysis of wing feather taxis in birds: Macroevolutionary patterns of genetic drift? Auk 119:943–954. Close ) indicating that a secondary has been lost evolutionarily between what we now term s4 and s5. Wings are broad and rounded (wing morphology usually p7 ~ p8 > p6 > p9 > p5 > p10 > p4 > p3 and with p4‒p10 notched and p4‒p9 emarginated; 3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close ); tail is squared. Geographic variation in appearance and molt strategies slight to moderate; see Systematics for differences between the two recognized subspecies. See Molts for molt and plumage terminology. The following is based primarily on plumage descriptions in Glutz von Blotzheim (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close ), Cramp and Simmons (3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close ), Forsman (11 Forsman, D. (1999). The Raptors of Europe and the Middle East. A Handbook of Field Identification. T & AD Poyser, London Close , 12 Forsman, D. (2016). Flight Identification of Raptors of Europe, North Africa and the Middle East. Bloomsbury, London, UK. Close ), and images in the Macaulay Library; see Duriez et al. (13 Duriez, O., B. Eliotout, and F. Sarrazin (2011). Age identification of Eurasian Griffon Vultures Gyps fulvus in the field. Ringing & Migration 26: 24–30. Close ) and Zuberogoitia et al. (14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ) for aging criteria for the Eurasian Griffon, and Pyle (15 Pyle, P. (2008). Identification Guide to North American Birds. Part II: Anatidae to Alcidae. Slate Creek Press, Point Reyes Station, CA, USA. Close ) for criteria of similar Accipitrine species. Sexes similar in appearance in all plumages; definitive appearance is usually assumed at the fourth to sixth basic plumage.

Natal Down

Present primarily April‒August. The first down is white, and molts after 18–35 d to a second down, which is cream-white on the underparts to pale gray on the upperparts (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close , 3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close , 16 Thaler, E., S. Maschler, and V. Steinkellner (1986). Vergleichende Studien zur Postembryonalentwicklung dreier Altweltgeier: Bartgeier, Schamtzgeier und Gänsgeier. Annalen des Naturhistorischen Museums in Wien. Serie B für Botanik und Zoologie 88–89B: 361–376. Close , 17 Elosegi, I. (1989). Vautour fauve (Gyps fulvus), Gypaete barbu (Gypaetus barbatus), percnoptere d’Egypte (Neophron percnopterus): Synthèse bibliographique et recherches. Acta Biologica Montana, Série documents de travail 3: 1–278. Close ).

Juvenile (First Basic) Plumage

Present primarily September‒May. Superficially similar to definitive basic plumage but the head and neck is covered by short white down. The ruff on the lower hindneck has lanceolated brown feathers that are up to 15 cm long. Upperwing median and lesser coverts and upperparts are pale brown to rufous-brown with pale shaft streaks, the mantle sometimes with a reddish color; these feathers are elongated and attenuated at the tips. The belly feathers have a contrasting clear rachis with brown vanes. Primaries, secondaries, and rectrices are uniform in wear and narrower than basic feathers, not showing mixed generations of remiges or molt clines (see Definitive Basic Plumage). Underwing coverts primarily light brown with pale shaft streaks, the greater coverts whitish and with dark centers to the inner feathers.

A study carried out in Hoces del Río Riaza Natural Park (Segovia, Spain) found a relationship between a nest's exposure to sunlight and the plumage color of nestlings. Nestlings from nests exposed to more sunlight developed paler plumages. It was also observed that fledgling females were paler than males (18 Fargallo, J. A., F. Martínez, K. Wakamatsu, D. Serrano, and G. Blanco (2018). Sex-Dependent Expression and Fitness Consequences of Sunlight-Derived Color Phenotypes. The American Naturalist 191(6): 726–743. Close ).

Formative Plumage

A Preformative ("Post-juvenile") Molt of scattered body feathers in December‒March, prior to commencement of the Second Molt, may exist in some individuals, as occurs in other Accipitrid and Buteo hawks (19 Pyle, P. (2005). First-cycle molts in North American Falconiformes. Journal of Raptor Research 39:378–385. Close ). Formative feathers occur at scattered locations on the upperparts and breast and would be fresher and intermediate in appearance between those of juvenile and definitive basic plumages (see image, below). Uniformly juvenile wing and tail feathers are retained.

Second to Fourth Basic Plumages

Present primarily August‒July. Following incomplete molts, body feathers show mixed generations, including retained juvenile feathers in Second Basic Plumage and occasionally in Third Basic Plumage. In Second Basic Plumage, occasionally all juvenile primaries are retained but more often from one to 5 inner primaries are replaced on each wing, contrasting with retained juvenile primaries among p3‒p10 (14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ). Up to 10 secondaries are also replaced, usually among the tertials, s1–s2, and s5–s6, following molt sequences typical of Accipitrine raptors and initiating Staffelmauser (see Molts). In Third Basic Plumage all primaries may be replaced or 1–4 juvenile outer primaries (among p7–p10) can continue to be retained among two waves or sets of basic inner primaries and 5–10 juvenile secondaries among s3–s4 and s7–s16 are almost always retained. In Fourth Basic Plumage, all juvenile primaries are replaced but some secondaries among s4 and s10–s13 may continue to be retained.

Variation in plumage and molt patterns recorded in the wild with banded individuals of known age in Grands Causses, France (13 Duriez, O., B. Eliotout, and F. Sarrazin (2011). Age identification of Eurasian Griffon Vultures Gyps fulvus in the field. Ringing & Migration 26: 24–30. Close ) and in central and northern Spain (14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ) indicate that individuals in Second–Fourth basic plumages largely retain a brown ruff with lanceolated feathers, increasingly mixed with beige and less-lanceolated feathers. In France, 91% of individuals in Second Basic Plumage had a brown lanceolated ruff, and 9% had a beige intermediate ruff, and these proportions changed to 80% and 20% in Third Basic Plumage and 63% and 37% in Fourth Basic Plumage (13 Duriez, O., B. Eliotout, and F. Sarrazin (2011). Age identification of Eurasian Griffon Vultures Gyps fulvus in the field. Ringing & Migration 26: 24–30. Close ). The beige feathers of the ruff were clearer and downy while the distal ends were brownish. Pointed scapulars were present in 80% of birds in Second Basic Plumage and in 22% of birds in Third Basic Plumage; there were no pointed scapulars in older birds (13 Duriez, O., B. Eliotout, and F. Sarrazin (2011). Age identification of Eurasian Griffon Vultures Gyps fulvus in the field. Ringing & Migration 26: 24–30. Close ). In these plumages, belly feathers showed contrast between the clear rachis and brown vanes.

Fourth to Seventh Basic Plumages

Present primarily September‒August. By these plumages, all juvenile flight feathers have typically been replaced and show Staffelmauser patterns as in Definitive Basic Plumage. Study of known-age birds in Grands Causses, France, indicate that the proportion of individuals with a white downy ruff increased to 19%, 27%, and 65% in the Fourth, Fifth, and Sixth basic plumages, respectively, while for birds in Seventh Basic Plumage, 85% had white downy ruff (13 Duriez, O., B. Eliotout, and F. Sarrazin (2011). Age identification of Eurasian Griffon Vultures Gyps fulvus in the field. Ringing & Migration 26: 24–30. Close ). Study of known-age birds in central and northern Spain produced similar results (14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ). In Fourth Basic Plumage, 18% of birds had a dark belly with no contrast between rachis and vanes, 50% in Fifth–Eighth basic plumages, and more than 80% after 10 years of age (13 Duriez, O., B. Eliotout, and F. Sarrazin (2011). Age identification of Eurasian Griffon Vultures Gyps fulvus in the field. Ringing & Migration 26: 24–30. Close ). The color of mantle feathers in Fourth–Seventh basic plumages may have reddish and brownish feathers, and more than 50% individuals after 10 years are pale.

Precise determination of plumages not determinable following the Third Prebasic Molt due to individual variation in maturation rates of the ruff feathering, molt rates, and other features.

Definitive Basic Plumage

Present primarily October‒September. Head and neck are covered with short, dense, pale brownish to creamy white feathers. A ruff of long, dense white down surrounds the base of the lower hindneck; some individuals in otherwise definitive appearance may show some beige feathering to the ruff (see above). The crop is covered with pale buff-brown to dark gray-brown feathers. Upperparts and underparts are pale yellow-brown to cream-brown. Upperwing median and lesser coverts are reddish-brown-gray to brownish-cream. Upperwing greater and primary coverts, primaries, secondaries, and rectrcies are blackish when fresh wearing to brownish when worn, the greater coverts and tertials usually with brownish-cream fringes or tips. Underwing primary and secondary coverts are yellowish-white with a large gray-brown point on each.

Incomplete molts usually result in mixed generations of body feathers and upperwing coverts producing a mottled appearance. Remiges can show 2‒4 sets of feathers in Staffelmauser (or stepwise) patterns (see Molts), the number of sets signifying minimum age (see 12 Forsman, D. (2016). Flight Identification of Raptors of Europe, North Africa and the Middle East. Bloomsbury, London, UK. Close , 20 Pyle, P. (2005). Remigial molt patterns in North American Falconiformes as related to age, sex, breeding status, and life-history strategies. Condor 107(4):823–834. Close , 14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ).

Aberrant Plumages

Partial leucistic (21 Camiña, A. (2005). A leucistic or partial albino Eurasian Griffon Vulture (Gyps fulvus). Vulture News 52:34. Close ) and albino (22 Herrero, F., D. Beltrán, and A. Camiña (2011). An albino Griffon Vulture Gyps fulvus in Spain. Vulture News 61:33–34. Close ) Eurasian Griffon have been recorded in Spain.

General

Molt and plumage terminology follows Humphrey and Parkes (23 Humphrey, P. S., and K. C. Parkes (1959). An approach to the study of molts and plumages. The Auk 76:1–31. Close ), as modified by Howell et al. (24 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: A review of molt and plumage homologies. The Condor 105:635–653. Close ). Under this nomenclature, terminology is based on evolution of molts along ancestral lineages of birds from ecdysis (molts) of reptiles, rather than on molts relative to breeding season, location, or time of the year, the latter generally referred to as “life-cycle” molt terminology (25 Jenni, L., and R. Winkler (2020). Moult and Ageing of European Passerines. Second edition. Bloomsbury, London, UK. Close ; see also 26 Pyle, P. (2022). Defining moults in migratory birds: A sequence-based approach. Journal of Avian Biology 2022:e02958. Close ). In north-temperate latitudes and among passerines, the Humphrey-Parkes (H-P) and life-cycle nomenclatures correspond to some extent but terms are not synonyms due to the differing bases of definition. Prebasic molts often correspond to “post-breeding“ or “post-nuptial“ molts (the Second Prebasic Molt often equating to the "first post-breeding molt," etc.) and preformative molts often correspond to “post-juvenile“ molts. The terms prejuvenile molt and juvenile plumage are preserved under H-P terminology (considered synonyms of first prebasic molt and first basic plumage, respectively) and the former terms do correspond with those in life-cycle terminology.

As in other large Accipitrine hawks, the Eurasian Griffon appears to exhibit a Complex Basic Strategy (cf. 24 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: A review of molt and plumage homologies. The Condor 105:635–653. Close , 27 Howell, S. N. G. (2010). Molt in North American Birds. Houghton Mifflin Harcourt, Boston, Massachusetts and New York, New York, USA. Close ), including incomplete prebasic molts and a limited preformative molt (19 Pyle, P. (2005). First-cycle molts in North American Falconiformes. Journal of Raptor Research 39:378–385. Close ), but no prealternate molts (3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close , 12 Forsman, D. (2016). Flight Identification of Raptors of Europe, North Africa and the Middle East. Bloomsbury, London, UK. Close , 14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close , 15 Pyle, P. (2008). Identification Guide to North American Birds. Part II: Anatidae to Alcidae. Slate Creek Press, Point Reyes Station, CA, USA. Close ).

Prejuvenile (First Prebasic) Molt

Complete, primarily May–August, in the nest. No detailed information on this molt in Eurasian Griffon.

Preformative Molt

Only recently recognized in Acciptrine hawks as separate from commencement of the Second Prebasic Molt (19 Pyle, P. (2005). First-cycle molts in North American Falconiformes. Journal of Raptor Research 39:378–385. Close ); in the Eurasian Griffon, this molt has not been confirmed (14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ), but a limited molt appears to occur in some (but not all) individuals in November–March (cf. 3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close ) as occurs in other large Accipitrine hawks (19 Pyle, P. (2005). First-cycle molts in North American Falconiformes. Journal of Raptor Research 39:378–385. Close , 15 Pyle, P. (2008). Identification Guide to North American Birds. Part II: Anatidae to Alcidae. Slate Creek Press, Point Reyes Station, CA, USA. Close ). In those species, the Preformative Molt can include up to 40% of body feathers but can be absent in some individuals; based on examination of Macaulay Library images it appears to occur to a limited extent in the Eurasian Griffon (see images under Plumages). No wing coverts or flight feathers are replaced during Preformative Molts in large Accipitrine hawks.

Second through Fourth Prebasic Molts

Incomplete, primarily May–October. Replacement of juvenile body feathers and upperwing coverts often incomplete, resulting in mixed juvenile and basic feathers in Second Basic Plumage. Sequence of flight-feather replacement as in Definitive Prebasic Molt. Following the Second Prebasic Molt, the outer 4–9 (often 6–7) juvenile primaries and corresponding primary coverts and 12–20 juvenile secondaries are usually retained, replaced secondaries usually being among the tertials, s1, s5, and perhaps s12 (14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ). Staffelmauser (stepwise) replacement patterns (28 Stresemann, E., and V. Stresemann (1966). Die Mauser der Vögel. Journal für Ornithologie 107, Sonderheft. Close , 20 Pyle, P. (2005). Remigial molt patterns in North American Falconiformes as related to age, sex, breeding status, and life-history strategies. Condor 107(4):823–834. Close , 29 Pyle, P. (2006). Staffelmauser and other adaptive strategies for wing molt in larger birds. Western Birds 37(3):179–185. Close , 15 Pyle, P. (2008). Identification Guide to North American Birds. Part II: Anatidae to Alcidae. Slate Creek Press, Point Reyes Station, CA, USA. Close ) ensue (see below), the Third Prebasic Molt, commencing where Second Prebasic Molt arrested, with new sequences sometimes commencing at p1 and the tertials. Following the Third Prebasic Molt, no to 4–5 juvenile outer primaries and 5–12 juvenile secondaries (among s3–s4 and s7–s17 can be retained. Occasionally 1–5 secondaries (likely among s4, s8–s9, and s14–s15) may be retained following the Fourth Prebasic Molt (14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ), among three generations of basic feathers. During these initial remigial molts, symmetry is usually maintained between the wings but patterns can begin to become asymmetrical following the Third or Fourth prebasic molts. On average, 36.5% of the primaries and 17% of the secondaries were replaced during the Second Prebasic Molt, 40% of the primaries and 48% of the secondaries were replaced during the Third Prebasic Molt, and 40% of the primaries and 37.5% of the secondaries were replaced during the Fourth Prebasic Molt (14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ).

Definitive Prebasic Molt

Incomplete, primarily April–November. Most to many body feathers, upperwing coverts, and rectrices are usually replaced every year, but many feathers may be retained; primaries and secondaries are only partially replaced every year. Primaries are replaced distally (p1 to p10), secondaries replaced proximally from s1, s5, and perhaps s12, and distally from the tertials (often bilaterally from the middle tertial, t2) , and rectrices may typically be replaced in sequence r1–r6–r3–r4–r2–r5 on each side of tail. Replacement among s10–s20 may be irregular or involve skipped feathers (cf. 30 Edwards, A. E., and S. Rohwer (2005). Large-scale patterns of molt activation in the flight feathers of two Albatross species. Condor 107(4):835-848. Close ), with consistent nodes possibly being maintained at s12 and s15 (14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ), but more study is needed. Upperwing greater coverts are molted simultaneously with their corresponding secondaries, as occurs with primary coverts and primaries. On average, adults molted 48.9% of the primaries and 56.1% of the secondaries in a given year (14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ).

Molting patterns among primaries and secondaries exhibit Staffelmauser (28 Stresemann, E., and V. Stresemann (1966). Die Mauser der Vögel. Journal für Ornithologie 107, Sonderheft. Close , 31 Clark, W. S., R. D. Chancellor, and B. U. Meyburg (2004). Wave moult of the primaries in accipitrid raptors, and its use in ageing immatures. In Raptors Worldwide: Proceedings of the VI World Conference on Birds of Prey and Owls (R. D. Chancellor and B. U. Meyersburg, Editors). World Working Group on Birds of Prey, Budapest, Hungary. pp. 795–804. Close , 20 Pyle, P. (2005). Remigial molt patterns in North American Falconiformes as related to age, sex, breeding status, and life-history strategies. Condor 107(4):823–834. Close , 29 Pyle, P. (2006). Staffelmauser and other adaptive strategies for wing molt in larger birds. Western Birds 37(3):179–185. Close , 15 Pyle, P. (2008). Identification Guide to North American Birds. Part II: Anatidae to Alcidae. Slate Creek Press, Point Reyes Station, CA, USA. Close ), whereby incomplete molts result is a series of commencement points, beginning with termination points of previous prebasic molt and also initiating new series commencing at p1, s1, s5, perhaps s12, and/or the tertials. Replacement thus typically proceeds in 2–4 (rarely 1 or 5) waves through the wing. After several years replacement patterns can become quite asymmetrical between the wings. Staffelmauser appears to be a product of insufficient time to undergo a complete wing-feather molt but has adaptive benefits in producing multiple small gaps in the wing during molt, which retains wing integrity and ability to fly and forage (32 Tucker, V. A. (1991). The effect of molting on the gliding performance of a Harris' Hawk (Parabuteo unicinctus). The Auk 108:108–113. Close , 33 Shugart, G. W., and S. Rohwer (1996). Serial descendant primary molt or Staffelmauser in Black-crowned Night-Herons. Condor 98(2):222–233. Close , 20 Pyle, P. (2005). Remigial molt patterns in North American Falconiformes as related to age, sex, breeding status, and life-history strategies. Condor 107(4):823–834. Close ).

Head and Neck

Skin is blackish under the down on the head and neck; skin on the rest of the body is pinkish-brown colored. Bare skin at the base of the neck is blue in adults, and more deeply colored when excited; it is completely bare in the area around the eye, and is light bluish. The cere is lead to blue-gray (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close ). The ring around the eye in nestlings is dark gray, and the eyelids are blue gray (3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close ).

Iris

The color of the iris changes with age (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close , 3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close ). Based on resightings of banded birds of a known age from Grand Causses, France (n = 204; 13 Duriez, O., B. Eliotout, and F. Sarrazin (2011). Age identification of Eurasian Griffon Vultures Gyps fulvus in the field. Ringing & Migration 26: 24–30. Close ) and from Vizcaya Province, Spain (n = 247; 14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ), the color of the iris was dark from the autumn of the first calendar year (1cy) to the spring of the 4cy, brown from the autumn of the 4cy to spring of the 6cy, brown-hazel from the autumn of the 6cy to spring of the 7cy, hazel from the autumn of the 7cy to spring of the 8cy, hazel-yellow from autumn of the 8cy to spring of the 9cy, and hazel to yellow after the autumn of the 9cy or spring of the 10cy.

Bill

In nominate Gyps fulvus fulvus, the color of the bill changes with age (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close , 3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close ). At hatching, the bill is pinkish and darkens from 8–11 d age (16 Thaler, E., S. Maschler, and V. Steinkellner (1986). Vergleichende Studien zur Postembryonalentwicklung dreier Altweltgeier: Bartgeier, Schamtzgeier und Gänsgeier. Annalen des Naturhistorischen Museums in Wien. Serie B für Botanik und Zoologie 88–89B: 361–376. Close ). Based on resightings of banded birds of a known age from Grand Causses, France (n = 204; 13 Duriez, O., B. Eliotout, and F. Sarrazin (2011). Age identification of Eurasian Griffon Vultures Gyps fulvus in the field. Ringing & Migration 26: 24–30. Close ) and from Vizcaya Province, Spain (n = 247; 14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ), the bill color was black from the autumn of the first calendar year (1cy) to spring of the 2cy, black, but with the front of the bill clear in some birds, from the autumn of the 2cy to spring of the 3cy, and the front of the bill was clear from the autumn of the 3cy to the spring of the 4cy. The clear area of the bill started to advance to both sides of the front of the bill from the autumn of the 4cy to the spring of the 5cy; the dark area was mainly present at the base of the bill from the autumn of the 5cy to the spring of the 7cy, was almost completely clear from the spring or autumn of the 7cy, and completely clear from the autumn of the 8cy autumn onwards (13 Duriez, O., B. Eliotout, and F. Sarrazin (2011). Age identification of Eurasian Griffon Vultures Gyps fulvus in the field. Ringing & Migration 26: 24–30. Close , 14 Zuberogoitia, I., J. De La Puente, J. Elorriaga, R. Alonso, L. E. Palomares, and J. E. Martínez (2013). The flight feather molt of Griffon vultures (Gyps fulvus) and associated biological consequences. Journal of Raptor Research 47(3): 292–303. Close ). In Gyps fulvus fulvescens, the bill is yellowish or greenish horny to dusky brown (34 Ali, S., and S. D. Ripley (1978). Handbook of the Birds of India and Pakistan. Volume 1. 2nd edition. Oxford University Press, Delhi, India. Close ).

Tarsi and Toes

In nominate fulvus, the tarsi and feet are brownish-gray to dirty blue-gray with black-gray claws (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close ). In subspecies fulvescens, the tarsi and toes are dirty yellow to greenish-gray (34 Ali, S., and S. D. Ripley (1978). Handbook of the Birds of India and Pakistan. Volume 1. 2nd edition. Oxford University Press, Delhi, India. Close ).

Linear Measurements

Total Length

• male, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 1,093 mm, range 1,064–1,144, n = 10 (Zuberogoitia, personal communication)
• female, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 1,108 mm, range 1,072–1,199, n = 8 (Zuberogoitia, personal communication)

Wingspan

• male, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 2,568 mm, range 2,326–2,656, n = 10 (Zuberogoitia, personal communication)
• female, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 2,674 mm, range 2,602–2,756, n = 4 (Zuberogoitia, personal communication)

Wing Length

• male, Europe and Tunisia, mean 725 mm, range 685–775 mm, n = 9 (3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close )
• male, Europe, mean 708.7 mm, range 684–735, n = 22 (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close )
• male, Crete Island, Greece, mean 695 mm ± 27.2 SD, range 640–750, n = 29 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• male, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 715.7 mm, range 656–757, n = 7 (Zuberogoitia, personal communication)
• female, Europe and Tunisia, mean 752 mm, range 725–775 mm, n = 9 (3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close )
• female, Europe, mean 707.7 mm, range 690–750, n = 15 (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close )
• female, Crete Island, Greece, mean 703 mm ± 28.4 SD, range 650–750, n = 22 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• female, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 725.6 mm, range 714–742, n = 6 (Zuberogoitia, personal communication)

Tail Length

• male, Europe, Tunisia, mean 300 mm, range 280–320 mm, n = 10 (3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close )
• male, Europe, mean 355.0 mm, range 310–395, n = 22 (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close )
• male, Crete Island, Greece, mean 300 mm ± 30.2 SD, range 24–35, n = 29 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• male, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 352.3 mm, range 341–362, n = 10 (Zuberogoitia, personal communication)
• female, Europe, Tunisia, mean 304 mm, range 280–320 mm, n = 8 (3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close )
• female, Europe, mean 353.3 mm, range 325–375, n = 15 (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close )
• female, Crete Island, Greece, mean 310 mm ± 27.9 SD, range 27.2–38, n = 22 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• female, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 353.1 mm, range 332–372, n = 9 (Zuberogoitia, personal communication)

Head Length

• male, Crete Island, Greece, mean 146.1 mm ± 3.92 SD, range 139.5–153.8, n = 29 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• male, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 152.2 mm, range 145–184, n = 10 (Zuberogoitia, personal communication)
• female, Crete Island, Greece, mean 138.9 mm ± 2.50 SD, range 134.3–143.2, n = 22 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• female, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 150.2 mm, range 147–153, n = 9 (Zuberogoitia, personal communication)

Head Width

• male, Crete Island, Greece, mean 62.1 mm ± 2.14 SD, range 58.4–66.1, n = 29 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• female, Crete Island, Greece, mean 59.8 mm ± 2.51 SD, range 57.3–66.8, n = 22 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )

Bill Length

• male, Europe, Tunisia, mean 52.2 mm, range 49–55 mm, n = 9 (3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close )
• male, Europe, mean 52.7 mm, range 50–55, n = 22 (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close )
• male, Crete Island, Greece, mean 54.1 mm ± 2.18 SD, range 49.9–61.1, n = 29 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• male, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 52.8 mm, range 50.0–55.0, n = 10 (Zuberogoitia, personal communication)
• female, Europe, Tunisia, mean 52.7 mm, range 51–56 mm, n = 9 (3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close )
• female, Europe, mean 52.1 mm, range 50–54, n = 15 (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close )
• female, Crete Island, Greece, mean 51.4 mm ± 1.81 SD, range 45.9–55, n = 22 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• female, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 52.4 mm, range 50.2–54.3, n = 9 (Zuberogoitia, personal communication)

Bill Width

• male, Crete Island, Greece, mean 24.8 mm ± 1.98 SD, range 21.4–29, n = 29 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• female, Crete Island, Greece, mean 25.3 mm ± 1.86 SD, range 21.8–29, n = 22 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )

Bill Depth

• male, Crete Island, Greece, mean 35.4 mm ± 1.64 SD, range 30.8–38.6, n = 29 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• female, Crete Island, Greece, mean 36 mm ± 1.90 SD, range 32.5–40, n = 22 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )

Tarsus Length

• male, Europe, Tunisia, mean 111 mm, range 107–117 mm, n = 10 (3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close )
• male, Europe, mean 105.6 mm, range 100–113, n = 22 (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close )
• male, Crete Island, Greece, mean 120.5 mm ± 9.67 SD, range 99.5–135.0, n = 29 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• female, Europe, Tunisia, mean 113 mm, range 107–119 mm, n = 9 (3 Cramp, S., and K. E. L. Simmons, Editors (1980). Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic. Volume II: Hawks to Bustards. Oxford University Press, Oxford, UK. Close )
• female, Europe, mean 108.2 mm, range 102–114, n = 15 (9 Glutz von Blotzheim, N., K. M. Bauer, and E. Bezzel (1971). Handbuch der Vögel Mitteleuropas. Band 4. Falconiformes. Akademische Verlagsgesellschaft, Frankfurt am Main, Germany. Close )
• female, Crete Island, Greece, mean 117.2 mm ± 8.42 SD, range 101–134, n = 22 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )

Mass

• male, Crete Island, Greece, mean 7.64 kg ± 0.69 SD, range 6.5–9, n = 29 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )
• male, Israel, mean 7.85 kg ± 0.16 SE, n = 15 (36 Spiegel, O., R. Harel, A. Centeno-Cuadros, O. Hatzofe, W. M. Getz, and R. Nathan (2015). Moving beyond Curve Fitting: Using Complementary Data to Assess Alternative Explanations for Long Movements of Three Vulture Species. The American Naturalist 185(2): E44-E54. Close )
• male, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 8.76 kg, range 7.4–10.4, n = 8 (Zuberogoitia, personal communication)
• female, Arreturas, Bizkaia Province, País Vasco Region, Spain, mean 8.63 kg, range 7.2–9.4, n = 9 (Zuberogoitia, personal communication)
• female, Israel, mean 8.51 kg ± 0.19 SE, n = 8 (36 Spiegel, O., R. Harel, A. Centeno-Cuadros, O. Hatzofe, W. M. Getz, and R. Nathan (2015). Moving beyond Curve Fitting: Using Complementary Data to Assess Alternative Explanations for Long Movements of Three Vulture Species. The American Naturalist 185(2): E44-E54. Close )
• female, Crete Island, Greece, mean 7.74 kg ± 0.42 SD, range 6.2–9, n = 22 (35 Xirouchakis S. M., and N. Poulakakis (2008). Biometrics, sexual dimorphism and gender determination of Griffon Vultures Gyps fulvus from Crete. Ardea 96(1): 91–98. Close )