Where does the frigate bird nest?

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).

FIgure 1. Fregata in flight.

FIgure 1. Fregata in flight. Note the narrow-chord wing membrane, as in all pterosaurs.

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.

FIgure 2. Fregata skull with a closeup of the tiny jugal.

FIgure 2. Fregata skull with a closeup of the tiny jugal.

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.

Figure 4. Skeleton of Fregata, the frigate bird. Note the long bill, long neck and long antebrachium, perhaps the closest living analog to Cretaceous ornithocheirid pterosaurs.

Figure 3. Skeleton of Fregata, the frigate bird. Note the long bill, long neck and long antebrachium, perhaps the closest living analog to Cretaceous ornithocheirid and pteranodontid pterosaurs (Fig. 5). Consider this a shoebill stork and/or pelican with a slender bill and very short legs and you will be close to its phylogenetic grade.

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.” 

Figure 2. Cearadactylus, Anhanguera and Pteranodon compared. The inset compares the humerus of Anhanguera and Pteranodon.

Figure 4. Cearadactylus, Anhanguera and Pteranodon compared. The inset compares the humerus of Anhanguera and Pteranodon. Compare proportions to the skeleton of Fregata. Look at those long wing tips, completely different from flightless pterosaurs, including large to giant azhdarchids. Most workers consider these taxa to be closely related, but the LRT does not confirm that.

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).

References
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.

wiki/Frigatebird

1 thought on “Where does the frigate bird nest?

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.