For a blog focused on pterosaurs
it sure took a long time to take a look at the extant frigate bird (Figs. 1-3; genus: Fregata), a modern analog for many of the sea-faring clades of pterosaurs in terms of wing shape (long span, short chord) and gliding ability (see below).
Between pelicans and cormorants
In the large reptile tree (LRT, 1227 taxa) the frigate bird nests between the clade Pelecanus + Balaeniceps (the shoebill) and Phalacrocorax (the cormorant). The shoebill has the longest legs in the clade, so it is the most primitive member. Most studies, including the LRT and DNA analyses, associate frigate birds with pelicans, skuas and petrels, but some link frigate birds with a larger list including herons, ibises, spoonbills, hamerkops, penguins, loons, gannets, and cormorants. Why can’t DNA be more specific? That’s a wide gamut of taxa. The LRT is specific and fully resolved.
Interesting that frigate birds don’t like to get wet
while their sisters, cormorants dive for food, but then have to stand with wings dripping while drying out. Distinct from ducks, cormorant feathers don’t shed water with an oily coat.
Fregata magnificens (Lacépède, 1799; up to 56 cm long) inflates its throat sac with air, like a balloon, to display its bright red color (distinct from the pelican throat sac, which fills with water and prey). According to Wikipedia, “frigatebirds spend most of the day in flight hunting for food, and roost on trees or cliffs at night. The duration of parental care is among the longest of any bird species; frigatebirds are only able to breed every other year. Fossils date back to the Eocene, 50 mya.”
Tested frigate birds
(Huey and Deutsch 2016) stayed aloft for two months without ever touching the ground riding cumulus thermals up to 6500 feet above sea level.
Like ornithocheirid and pteranodontid pterosaurs
the torso is small and the wing has a narrow chord and a wide span in Fregata. This is also like modern man-made gliders, and unlike the proportions found in large to giant azhdarchids, which could not fly at all, contra traditional thinking, based on their relatively short distal wing finger phalanges (like those of small flightless pterosaurs).
Huey RB and Deutsch C 2016. How frigate birds soar around the doldrums. Science 353 (6294):26–27.
Lacépède BGÉ de 1799. Discours d’ouverture et de clôture du cours d’histoire naturelle : donné dans le Muséum national d’Histoire naturelle, l’an VII de la République, et tableaux méthodiques des mammifères et des oiseaux, Paris.