The final word on the Cypseloides swifts
Kevin Easely chimes in about the swifts. His verdict: White-chinned Swifts all along.
Some nice photos of swifts coming out of Panama of late. We always suspected here in CR that Spot-fronted Swifts were in Panama as we have seen them VERY close to the border on both the Caribbean side and the Pacific side (photos as well). Just a matter of time really and getting people in the field that are not only familiar with swifts but actually take the time to identify them. Most of the clients I get just want to tick the species of swifts and don't want to study them thoroughly. We have made it a mission to study swifts here in CR and have come up with 10 times the data over the past 5 years than was ever present. All of my guides are nuts for swifts now...and photograph them as much as they can.
Regarding the White-chinned vs Black Swift conversation...I am convinced that all of the photos in question are White-chinned Swift. Not so much based on the nostril size...but on plumage and shape. White-chinned has a big head which we refer to here in CR as bull-headed and also has a short necked. The projection of the head from the body is short overall. It is a shorter bird in length giving it a thick-bodied look. The wings are shorter and a bit more broad as well, very different from Black Swift which has a longer and thinner neck, longer vent, longer tail and longer body overall giving it a slimmer appearance while still being a large, stout swift. Even the photo labeled as..."this is a Black Swift"...I believe to be a White-chinned Swift. Overall coloration can be seen clearly on the bird in flight labeled Black Swift and especially on the bird on the nest and it is dusky gray supporting White-chinned...not blackish as in Black Swift. Facial markings support White-chinned as well with the pale spot behind the eye. There is nothing I can see in the photos to suggest otherwise.
I didn't want to get overly involved in this but at the same time when the consensus was leading toward Black Swift I felt I should weigh in. Granted, swift identification is very challenging and proper photos are necessary...which they were able to get.
As far as shape goes...Spot-fronted and White-chinned have a similar overall shape...bull-headed, short bodied, broader-winged etc. The shape of the Black Swift is more in line with White-collared, perhaps with Black Swift being slightly more compact. Head projection and size of head are very similar.
I would personally try to get the conversation over to White-chinned...which based on your recent comments you are doing, Kudos for that. I know that birders can get quite sensitive over things like this but the important thing is to get it right.