Why would the blue-footed booby be treif? I can't see anything that would make it not kosher, and the Torah does not mention it (obviously) in the list of forbidden birds in Vayikra 11:13-19.
2Who said it wasn't kosher? (I'm not saying that it is)– MTLMay 4, 2017 at 4:40
1Perhaps they are a type of "seagull" or "pelican"?– Double AA ♦May 4, 2017 at 15:30
related: judaism.stackexchange.com/questions/22315/… ; judaism.stackexchange.com/questions/76150/… ; judaism.stackexchange.com/questions/82300/… ; judaism.stackexchange.com/questions/67041/are-songbirds-kosher– LoewianMay 4, 2017 at 15:32
@kouty treif is colloquially used to mean "not kosher," in a general sense.– Isaac Moses ♦May 4, 2017 at 20:52
1@isaa fwiw I disagree with the rollback– Double AA ♦May 4, 2017 at 21:13
First off, let me say that you have purposed an excellent question. See this fine article. The quotation below is taken from it.
The Torah, in Parshas Shmini, when informing us of the kashrus status of animals, lists specific types of birds that are not kosher. Ultimately, through derivation of the various “l’mineihu” words found in that section, Chazal (Chullin 63b, Rambam, Ma’achalos Assuros 1:14) identify 24 classes of birds that are not kosher, each one with many species. Any bird that is not from one of these 24 classes is kosher (Rashi, Chullin 61a d”h oaf, Shulchan Aruch YD 82:1). The problem is, however, that we can no longer identify the non-kosher birds that are mentioned.
The simple answer is that we do not have a tradition that the blue-footed booby is kosher, so we abstain from eating it because there is a small chance that it might be one of the forbidden fowls.
Comments are not for extended discussion; this conversation has been moved to chat.– msh210 ♦May 6, 2017 at 18:37