Just curious as to which type of bird has the easiest time flying. The one that can take off and stay aloft with the least effort?
The reason I ask is because in my area, I often see hawks just soaring around in circles, not flapping their wings, just riding the thermal wave up.
On the other hand, we also have fat quails, which travel mostly by running around. Oh sure, they’ll fly if you spook them, but only far enough to get away.
Well, I don’t know about ease of flying, but hummingbirds have a few abilities lacked by larger avians - hovering and flying backwards.
Well, ease of taking off and ease of staying aloft are two very different things. In fact, they’re almost opposite.
Probably the masters at staying in the air the longest with the least effort are albatrosses. They make use of updrafts off the oceans surface to soar at low altitude. It is thought that some individuals may literally spend years in flight, even sleeping on the wing, as they circle the southern oceans. However, it can be very hard for an albatross to take off from land - they usually need a very stiff wind to get aloft.
Vultures are also very good at effortless soaring, using thermals to stay aloft on motionless wings. On migration, Turkey Vultures may fly thousands of miles while hardly flapping their wings at all, except when they take off each morning. (There are no thermals at night.)
The most maneuverable bird is certainly the hummingbird, but their acrobatics use up a lot of energy and they are not efficient.
Swifts are also highly aerial, although like hummers they use a lot of energy in flapping flight. Some species not only sleep in flight, the also mate in mid-air.
Quail are adapted for short, powerful take-offs to escape from ground predators. They are very good at launching themselves, but poor at staying up.
If “ha[ving] the easiest time flying” and hence being “the best flyer” is defined as the OP implies, with a minimal of actual energy expenditure and a maximal of use of wind, thermals, etc., then the answer would be “among the Procellariformes” – which may be a bit less than useful to those not fond of ornithology. But that order of birds includes the albatrosses, gooney birds, and the related forms that typically stay aloft for days (or, allegedly, even weeks) at a time over the ocean, depending on thermals and other winds customarily found above the open ocean.
It is worth noting, however, that “best flyer” may mean a variety of things depending on context – the special skills of hummingbirds, as noted by Speaker, the ability to stoop of some raptors, maximum speed capability, most agile at flying in tight spaces, etc.
Well, I suppose I meant most effortless flyer. That bird who’s body is designed to stay aloft with the least amount of effort.
What about the Arctic Tern? They are the champs at long distance fliers.
Agreed - albatrosses are probably the champions here. They do make use of updrafts, but they rely even more on dynamic soaring, which means that they exploit differences in wind speeds and don’t actually need any updrafts to stay aloft. (Note that radio-controlled sailplanes have recently been exploiting “DS” successfully.)
A colony of Laysan albatrosses nests on Kauai in Hawaii. When some of these birds were equipped with satellite tracking devices, it was learned that they regularly make round trips to near San Francisco for food.
A little bit off topic, but did you know that Puffins can fly? Puffins are those funny looking birds that look something like penquins. (who can’t fly)
A canard, Peanuthead. Penguins can indeed fly – but not in air. However, their mode of propulsion in water is not any of the normal “swimming” techniques used by other aquatic animals, but rather they “fly” underwater – i.e., they use their forelimbs (wings/flippers) for propulsion in much the way that flying birds do in the air.
Minor cavil – but that’s part of the fun of this board! 
Can I be the first to say “an unladen swallow”
agreed too
the program which ran on BBC ‘the flight of the condor’ also indicated long uninterrupted periods in the air
but the albatross must be the champ.
The frigatebird is the one that can fly the easiest because they have the largest wingspan to body ratio. But they have a REALLY hard time getting off the ground. Albatrosses are a close second because they just have a really large wingspan in general.
African or European? 
Can zombies fly?
We hadn’t specifically mentioned fastest here. The peregrine falcon can achieve 200 mph in a dive. But that’s not level flight. Looking it up, I’m a tad surprised at the top 10 fastest birds in level flight, at least according to this list:
Some variety of swift (white throated needletail) gets the top place. OK, but frigate birds, geese and ducks? A mallard was clocked at 65 mph? Really? With how stiff a tailwind?
Aside - can we retrieve some respect for class mammalia here? How do the most maneuverable species of bats compare to hummingbirds on that score?
What’s all this about the albicore? They’re heavy, too, I guess.
The real question: what flavor are they?
Wow! Learn something every day.
Perhaps some albatross flying when Colibri posted this is still circling the southern oceans? 
Jonathan Livingston Seagull.
Sheesh people.