THE BIRDS OF THE GULF OF MEXICO' 



By George H. Lowery, Jr., and Robert J. Newman, Museum of Zoology, Louisiana State University 



Birds are unlike any other class of animals in 

 their relationship to water as an environment. 

 Although some of them are absolutely dependent 

 upon the sea for their existence, none of them is a 

 creature of that medium in the same sense that a 

 marine invertebrate is, or even a marine mammal 

 such as a whale. All sea birds come to land to 

 nest; and, in North America, all of them spend a 

 part of their lives in the air. The birds of the 

 Gulf of Mexico are thus, without exception, 

 adapted to at least two media and endowed with 

 a mobility that frequently makes their spacial and 

 ecological classification difficult. None of them 

 is wholly "pelagic" in the narrowest sense, and 

 none of them wholly "littoral." 



To make matters more difficult, the area de- 

 limited b_v the salt water of the Gulf of Mexico as 

 it twice daily moves landward over the shores of 

 the North American continent and up the tidal 

 estuaries is a somewhat vague one. Its ill-defined 

 boundaries have been crossed, and are daily being 

 crossed, by hundreds of different kinds of birds. 

 The overwhelming majority of these birds are 

 really birds of the mainland, whose occurrence on 

 the Gulf is wholly marginal. As a result, the 

 Gulf and its tidal reaches present a vast interior 

 surface, with a very limited avifauna, contained 

 within a narrow rim around which birds occur in 

 profusion. 



This distributional pattern introduces serious 

 problems when one attempts to summarize the 

 bird life of the Gulf of Mexico, problems that are 

 not encountered in the same degree in the case of 

 more sedentary groups of animals, or even in the 

 case of the avifauna of terrestrial regions. The 

 conventional summary of the bird life of a land 

 area seeks to review all the species that have been 

 known to occur there, to provide the visitor to 

 that area with a reference to the status of every 

 bird that he is likely to observe. As long as we 

 are dealing with the waters of the open Gulf, we 



1 Manuscript submitted for publication March 1952. 



can employ much the same approach, mentioning 

 all the species that have been found offshore. But 

 the moment we turn to the intertidal zone, such a 

 treatment becomes impossible. Too many of the 

 records on which our judgments must be based do 

 not include information on the proximity of the 

 bird to tidewater. And, even if such information 

 were available, the comprehensive approach would 

 scarcely be desirable, for it would lead to a survey 

 in which only a minor part of the species considered 

 would be birds that are regularly and intimately 

 associated with the Gulf itself. 



Since birds differ so tremendously in their rela- 

 tionships with water and since their relevance to a 

 discussion of the Gulf avifauna is so variable in 

 degree, we have divided the species that we shall 

 consider into three groups, each of which will be 

 accorded a different type of treatment. These 

 groups are: I. Offshore Birds; II. Birds of the 

 Coast; III. Land Birds Over the Open Gulf. 



Groups I and III, it will be noted, both chiefly 

 represent the main expanse of the Gulf of Mexico, 

 a portion of the earth's surface whose bird life 

 has never been comprehensively reviewed. We 

 have tried to mention every species in these groups 

 in order to make the corresponding sections of the 

 chapter a fairly complete reference source for bird 

 students traveling on the open Gulf. The avail- 

 able data concerning land birds offshore can con- 

 veniently be compressed into tabular form, and 

 this has been done. The status of the so-called 

 pelagic species, on the other hand, being more 

 complex, requires fuller discussion. 



The birds of the littoral present a fundamentally 

 different situation, since they cannot be defined 

 in concrete spacial terms. Completeness becomes 

 a less important concern in this group for reasons 

 later to be emphasized. Consequently we have 

 not hesitated to omit some species that have actu- 

 ally come in contact on occasion with the water 

 of the Gulf itself. Even so, our list of coastal 

 species is so long that, in order to adapt the ac- 



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