Tropicbirds' phylogeny is a great point of contention: some researchers assert they are most closely related to Pelecaniformes (the order of seabirds that includes pelicans, cormorants, gannets and boobies, to which Tropicbirds bear superficial physical resemblance), while others suggest that are their own monophyletic order, Phaethontiformes, perhaps sharing recent ancestry with Procellariiformes (the order that includes petrels and albatrosses). Tropicbirds' life history patterns are certainly very similar to those of many Procellariiformes (and some Pelecaniformes, especially the gannets): they exhibit a high degree of site fidelity and philopatry (returning to the site of their birth to breed, a sensible option for wandering species with sparse population density), they have long incubation and chick rearing times (about 90 days from chick to fledgling, similar to a gannet or a Hydrobatidae storm-petrel), and their chicks are altricial and have to spend time living on the water before they can lose enough weight to take flight (another characteristic of gannets). Tropicbirds are not sexually dimorphic, as many Procellariformes are (such as the petrels of the Macronectes genus – in some species, females are less than 80% the weight of males). Many aspects of tropicbirds' physiology are rather unique: they are totipalmate birds (with four webbed toes, as are all Pelecaniformes), but they are not excellent swimmers. They dive into the water at high speeds to catch their prey, which includes fish and the occasional squid. They are highly maneuverable fliers with a low wing aspect ratio (wing span to wing breadth); not only does this factor into their spectacular airborne mating displays, but it also allows them to elude parasitic seabirds that would harass them and force them to give up semi-digested food in their crop.
The White-bellied sea eagle actually makes up a superspecies with Sanford's Sea Eagle (Haliaeetus sanfordi). The two are sympatric (H. sanfordi is distributed throughout the Solomon Islands, its range entirely enclosed within the range of H. leucogaster) and very similar in morphology and coloration, although as with many avian superspecies there are key differences, mostly in coloration, that allow us to distinguish between species and are most probably the result of reinforcing selection favoring the maintenance of reproductive barriers. The two species show only a 0.3% genetic divergence in the nucleotide sequences of the genes for their cytochrome proteins, indicating a vey recent divergence.
White-bellied Sea Eagles are particularly notable for their hunting habits, which involve snatching a sea snake (family Hydrophiinae) out of the ocean (relying on sight and knowledge of fish spawning sites, diving in at an angle so as to avoid casting a shadow on the water's surface), carefully avoiding the snake's venomous, rhabdomyolysis-inducing bite, and carrying it to their nests, where they rip it apart and feed it to their semi-altricial chicks (which may remain in the nest for up to 80 days).
A note on pronunciation: there is continuing controversy over whether or not plover should be pronounced "PLUH-ver", like "lover", or "PLO-ver", like "clover". If you must refer to them as something other than Charadrians, I heartily recommend the latter; it's a much more satisfying sound.
The Pacific Golden Plover (Pluvialis fulva) and the three other members of the genus Pluvialis (the four species are physiologically very similar and they all have the same jet-black ventral coloration and sandy dorsal coloration) are quite fascinating in a number of ways. They feed on a particularly large range of food items, including berries, and they catch food in what's called a "run-pause-snatch" foraging technique, which works pretty much just like it sounds. In addition to being notably fast and deft on their feet, these plovers are very powerful fliers. P. fulva spends its winters wandering around the Indian Ocean, but come spring it flies halfway around the globe to spend its summer breeding and raising young in the tundra of western Alaska (as seen in the photo above).
Learn more about seabird behavior in this earlier post. You'll notice mention of Wisdom, the 63 year-old albatross that has flown the equivalent of a trip to the moon and back multiple times. Good news: she just laid her 35th egg! Congratulations, Wisdom, and safe flying.