Mark B Bartosik
Well-known member
Presumably 2 Cayenne Terns (or Cabot’s x Cayenne hybrids) – April 9, 2015 – Texas Upper Coast; Galveston County
Hi All,
Published Cayenne Tern records in North America are quite scarce. Only a few records and only single birds mostly found in North Carolina. Same in eBird database; it shows mostly published records. Entered are records from North Carolina and single records in four other states: Virginia (no photo and description say “rather” adult than juvenile Sandwich [yellow billed fledglings are quite common, at least on Texas shore; pers. obs.] – summarizing that this record is tentative), New York (published record), Louisiana (photo taken but not available to check, description included) and two records in Texas (apparently of the same bird; two locations close to each other, seen a week apart; no photo or description but for some reason confirmed by eBird). I read with interest Florida Records Committee reports about one as they called Cayenne-type tern found in 2012. It seems that they suspect hybrid possibility in every Cayenne even with all yellow bills. To my knowledge in Texas nobody even report/review subspecies so no need to worry. As races of any bird, no matter how ‘exotic’ they might be, are not on a birders’ tick list and anybody with minimal effort can tick off a Cabot’s around here there is no special interest to either keep checking flocks of hundreds/thousands Cabot’s Terns or chase one. As I have a special interest in terns any Cayenne or Cayenne-type tern vagrant always will be a very interesting find, at least to me.
So here we are; according to Junge and Voous (1955) Cayenne Terns from Caribbean populations may show considerable black on the bill while all-yellow bills predominate in the southern part of the breeding range in South America. Olsen and Larsson (1995) note that Cayenne is as Sandwich Tern acuflavida, but bill yellow, varying from orange to straw-yellow, often with darker central areas. They also regard phenotypically intermediate individuals, with the basal two-thirds or more of the bill black (thus approaching the condition in acuflavida), as referable to eurygnatha. Included photos (numbers 57-59 and 71 analyzed by Mitra and Buckley (2000) that also included excellent review of all published papers) show considerable variation in bill color and structure, even within the same flock. Major bill color-states (not discrete, but variable) include black with a yellow tip, black with yellow blotches, greenish-yellow with black blotches, orange-yellow with black blotches, pure greenish-yellow, and pure orange (red). Similarly, bill structure varies from as slender as acuflavida to almost as heavy as maxima, and from essentially straight to conspicuously drooping, but none of this variation has been critically dissected by sex, age, or latitude heeding area.
Hayes (2004) in his paper included a few sets of photographs illustrating bill variations and also stated that “The taxonomic relationship between Sandwich and Cayenne Terns is poorly understood. If any reproductive isolating mechanism exists between the two taxa, it may be based on bill coloration or, perhaps more likely, postural and vocal displays (P A. Buckley, pers. comm.). However, no behavioral differences between the taxa have been described. As for bill coloration, the crux of the issue is whether individuals with phenotypically "intermediate" bill coloration represent (1) variant (or even normal) phenotypes of Cayenne Tern, (2) the results of interbreeding between the two taxa, or (3) a mixture of both phenomena. A second crucial question is whether individuals indistinguishable from Sandwich Terns nesting in the southern Caribbean and eastern Brazil represent (1) Sandwich Terns or (2) variant Cayenne Tern phenotypes.
Perhaps I should mention that there are some private opinions posted on the web speculating that yellow with some black billed Sandwich Terns they claim to saw are, in their opinion, nothing else than Cabot’s with an aberrant bill – but … no photos were taken. If we are to take statements like that seriously than intermediate individuals here and in South America will ‘become’ Cabot’s and if we reverse the approach why not all Cabot’s Terns are being Cayenne with aberrant bill. On the other hand, the later possibility, but only applied to some Cabot’s-like individuals in South American breeding colonies, was pointed by Hayes (2004) in form of the second crucial question in point 2 (see paragraph above).
So here I have a question that most likely is never going to be answered, or better said one answer is not going to be approved by all. Are the birds I saw from the South American race eurygnatha or they are Cabot's X Cayenne Tern hybrids with intermediate bill coloration? BTW from the point of my interest in terns I would love these birds to be a Cabot’s Terns with aberrant bills but as there is not, to my best knowledge, any published studies describing documented cases of such birds so I see this as an unlikely possibility. I remember reading somewhere on the web that a few Cabot’s with very little extra yellow spots were seen in North Carolina but even in those cases hybrid possibility was proposed as this area is known for Cayenne Terns to show up from time to time in the past so these vagrants could stay there and breed injecting their genes to Cabot’s population gene pool. In Texas I saw thousands of Cabot’s and never saw one before with anything suggesting any extra yellow areas in the bill coloration. It might be worth to mention that every time I check tern flocks I am mostly looking at primaries and bills of as many birds as possible; for other reasons than trying to find a different species/race but it sometimes help with that as well. The Cayenne numbered #2 has only small patch of yellow (it is more like orange comparing to the bill tip coloration; this is characteristic to some Cayenne bill coloration) at the base of maxilla; no photos of other bill’s part were taken, from different angles, reason at the end of this post, but I assume bill coloration was similar on another side. I would like to know what coloration of the mandible ventral part is. Also bill tip coloration: in Cabot’s there is a sharp defined border between yellow and black areas. As we can see in Cayenne #2 the maxilla tip yellow part ends farther from the bill tip than in mandible and there is no fine definition line between yellow and black but rather yellow smudges into the black area (also rather typical to Cayenne intermediates). Well, I have to admit that if I only found bird #2 I will probably had a huge headache by now. The fact that both these terns were part of the same flock let me assume that they could come from the same wintering ground in the South and are traveling together. Both birds have bills coloration matching some individuals in photo collection of intermediates published by Hayes (2004).
Crude measurements of bill depth at the base indicate that Cayenne #1 bill has the same depth as one Cabot’s and is slightly broader compare to a couple other Cabot’s in the flock, and slightly shorter in total length in comparison to one (I have no other adequate photos taken to take more reasonable measurements).
Photos Cayenne #1
On the wing
http://www.pbase.com/mbb/image/159764477
Between Cabot’s and other birds
http://www.pbase.com/mbb/image/159764483
http://www.pbase.com/mbb/image/159764485
Comparison of bill structure and coloration with other Thalasseus terns I found in Texas
http://www.pbase.com/mbb/image/159764475/original
Ventral bill view to show mostly yellow coloration of mandible ventral part
Dorsal bill view to show mostly yellow coloration of maxilla dorsal part
Lateral bill view to show distribution of the yellow and black coloration of maxilla and mandible lateral parts (right side having more black area than left one)
http://www.pbase.com/mbb/image/159764474/original
Cayenne #2
http://www.pbase.com/mbb/image/159764487
All these photos from above and several more can be check in one folder when following this link (to see composite photo in full resolution it might be necessary to click on ‘original’ under the photo if clicked in folder; links above are to full resolution)
http://www.pbase.com/mbb/cayenne_terns_2___april_9_2015__texas_upper_coast
Note about sighting: This day was one of first few days when very large influx of migrating Cabot’s Tens occurred. With extreme high tide during part of that day birds had only a very few spots available to rest. Well, beaches are public and good people need a rest and relax. I usually try to find secluded places but you cannot expect that good birds will only show up in such places. It is a migration time so there are plenty of not only birds on the beaches but plenty of people as well. Unfortunately because of high tide and limited available resting spots these huge flocks of birds were easy to spook and some kept leaving the area when disturbed. Finally when too many people came to the beach and walkers, and moving vehicles were stressing birds too much the majority of birds left the area, so did I. Usually when the whole flock is spooked and fly away it will find spot to rest somewhere else and will not come back. I tried to relocate these terns during next few days, including spots even far away (where I know terns like to rest) – no success. Terns are on the move and only few of Cabot’s Terns will nest around here. It could be interesting if a few Cayenne Terns (hybrids, or whatever somebody wants to call them) start to nest here in Texas too so interbreeding with Cabot’s could take place right around the corner where I live.
All published papers I mentioned in this post are easy to get on the web but if somebody have problem to locate them I can email a link or a pdf copy (of course not a Olsen and Larsson book)
Cheers,
Mark
Hi All,
Published Cayenne Tern records in North America are quite scarce. Only a few records and only single birds mostly found in North Carolina. Same in eBird database; it shows mostly published records. Entered are records from North Carolina and single records in four other states: Virginia (no photo and description say “rather” adult than juvenile Sandwich [yellow billed fledglings are quite common, at least on Texas shore; pers. obs.] – summarizing that this record is tentative), New York (published record), Louisiana (photo taken but not available to check, description included) and two records in Texas (apparently of the same bird; two locations close to each other, seen a week apart; no photo or description but for some reason confirmed by eBird). I read with interest Florida Records Committee reports about one as they called Cayenne-type tern found in 2012. It seems that they suspect hybrid possibility in every Cayenne even with all yellow bills. To my knowledge in Texas nobody even report/review subspecies so no need to worry. As races of any bird, no matter how ‘exotic’ they might be, are not on a birders’ tick list and anybody with minimal effort can tick off a Cabot’s around here there is no special interest to either keep checking flocks of hundreds/thousands Cabot’s Terns or chase one. As I have a special interest in terns any Cayenne or Cayenne-type tern vagrant always will be a very interesting find, at least to me.
So here we are; according to Junge and Voous (1955) Cayenne Terns from Caribbean populations may show considerable black on the bill while all-yellow bills predominate in the southern part of the breeding range in South America. Olsen and Larsson (1995) note that Cayenne is as Sandwich Tern acuflavida, but bill yellow, varying from orange to straw-yellow, often with darker central areas. They also regard phenotypically intermediate individuals, with the basal two-thirds or more of the bill black (thus approaching the condition in acuflavida), as referable to eurygnatha. Included photos (numbers 57-59 and 71 analyzed by Mitra and Buckley (2000) that also included excellent review of all published papers) show considerable variation in bill color and structure, even within the same flock. Major bill color-states (not discrete, but variable) include black with a yellow tip, black with yellow blotches, greenish-yellow with black blotches, orange-yellow with black blotches, pure greenish-yellow, and pure orange (red). Similarly, bill structure varies from as slender as acuflavida to almost as heavy as maxima, and from essentially straight to conspicuously drooping, but none of this variation has been critically dissected by sex, age, or latitude heeding area.
Hayes (2004) in his paper included a few sets of photographs illustrating bill variations and also stated that “The taxonomic relationship between Sandwich and Cayenne Terns is poorly understood. If any reproductive isolating mechanism exists between the two taxa, it may be based on bill coloration or, perhaps more likely, postural and vocal displays (P A. Buckley, pers. comm.). However, no behavioral differences between the taxa have been described. As for bill coloration, the crux of the issue is whether individuals with phenotypically "intermediate" bill coloration represent (1) variant (or even normal) phenotypes of Cayenne Tern, (2) the results of interbreeding between the two taxa, or (3) a mixture of both phenomena. A second crucial question is whether individuals indistinguishable from Sandwich Terns nesting in the southern Caribbean and eastern Brazil represent (1) Sandwich Terns or (2) variant Cayenne Tern phenotypes.
Perhaps I should mention that there are some private opinions posted on the web speculating that yellow with some black billed Sandwich Terns they claim to saw are, in their opinion, nothing else than Cabot’s with an aberrant bill – but … no photos were taken. If we are to take statements like that seriously than intermediate individuals here and in South America will ‘become’ Cabot’s and if we reverse the approach why not all Cabot’s Terns are being Cayenne with aberrant bill. On the other hand, the later possibility, but only applied to some Cabot’s-like individuals in South American breeding colonies, was pointed by Hayes (2004) in form of the second crucial question in point 2 (see paragraph above).
So here I have a question that most likely is never going to be answered, or better said one answer is not going to be approved by all. Are the birds I saw from the South American race eurygnatha or they are Cabot's X Cayenne Tern hybrids with intermediate bill coloration? BTW from the point of my interest in terns I would love these birds to be a Cabot’s Terns with aberrant bills but as there is not, to my best knowledge, any published studies describing documented cases of such birds so I see this as an unlikely possibility. I remember reading somewhere on the web that a few Cabot’s with very little extra yellow spots were seen in North Carolina but even in those cases hybrid possibility was proposed as this area is known for Cayenne Terns to show up from time to time in the past so these vagrants could stay there and breed injecting their genes to Cabot’s population gene pool. In Texas I saw thousands of Cabot’s and never saw one before with anything suggesting any extra yellow areas in the bill coloration. It might be worth to mention that every time I check tern flocks I am mostly looking at primaries and bills of as many birds as possible; for other reasons than trying to find a different species/race but it sometimes help with that as well. The Cayenne numbered #2 has only small patch of yellow (it is more like orange comparing to the bill tip coloration; this is characteristic to some Cayenne bill coloration) at the base of maxilla; no photos of other bill’s part were taken, from different angles, reason at the end of this post, but I assume bill coloration was similar on another side. I would like to know what coloration of the mandible ventral part is. Also bill tip coloration: in Cabot’s there is a sharp defined border between yellow and black areas. As we can see in Cayenne #2 the maxilla tip yellow part ends farther from the bill tip than in mandible and there is no fine definition line between yellow and black but rather yellow smudges into the black area (also rather typical to Cayenne intermediates). Well, I have to admit that if I only found bird #2 I will probably had a huge headache by now. The fact that both these terns were part of the same flock let me assume that they could come from the same wintering ground in the South and are traveling together. Both birds have bills coloration matching some individuals in photo collection of intermediates published by Hayes (2004).
Crude measurements of bill depth at the base indicate that Cayenne #1 bill has the same depth as one Cabot’s and is slightly broader compare to a couple other Cabot’s in the flock, and slightly shorter in total length in comparison to one (I have no other adequate photos taken to take more reasonable measurements).
Photos Cayenne #1
On the wing
http://www.pbase.com/mbb/image/159764477
Between Cabot’s and other birds
http://www.pbase.com/mbb/image/159764483
http://www.pbase.com/mbb/image/159764485
Comparison of bill structure and coloration with other Thalasseus terns I found in Texas
http://www.pbase.com/mbb/image/159764475/original
Ventral bill view to show mostly yellow coloration of mandible ventral part
Dorsal bill view to show mostly yellow coloration of maxilla dorsal part
Lateral bill view to show distribution of the yellow and black coloration of maxilla and mandible lateral parts (right side having more black area than left one)
http://www.pbase.com/mbb/image/159764474/original
Cayenne #2
http://www.pbase.com/mbb/image/159764487
All these photos from above and several more can be check in one folder when following this link (to see composite photo in full resolution it might be necessary to click on ‘original’ under the photo if clicked in folder; links above are to full resolution)
http://www.pbase.com/mbb/cayenne_terns_2___april_9_2015__texas_upper_coast
Note about sighting: This day was one of first few days when very large influx of migrating Cabot’s Tens occurred. With extreme high tide during part of that day birds had only a very few spots available to rest. Well, beaches are public and good people need a rest and relax. I usually try to find secluded places but you cannot expect that good birds will only show up in such places. It is a migration time so there are plenty of not only birds on the beaches but plenty of people as well. Unfortunately because of high tide and limited available resting spots these huge flocks of birds were easy to spook and some kept leaving the area when disturbed. Finally when too many people came to the beach and walkers, and moving vehicles were stressing birds too much the majority of birds left the area, so did I. Usually when the whole flock is spooked and fly away it will find spot to rest somewhere else and will not come back. I tried to relocate these terns during next few days, including spots even far away (where I know terns like to rest) – no success. Terns are on the move and only few of Cabot’s Terns will nest around here. It could be interesting if a few Cayenne Terns (hybrids, or whatever somebody wants to call them) start to nest here in Texas too so interbreeding with Cabot’s could take place right around the corner where I live.
All published papers I mentioned in this post are easy to get on the web but if somebody have problem to locate them I can email a link or a pdf copy (of course not a Olsen and Larsson book)
Cheers,
Mark
