of one species of tortoise, two species of lizards, at least one
(unidentified) species of snake, 49 species of birds (48 recorded by us
and the Semipalmated Sandpiper), and 12 species of mammals. This is
clearly a depauperate fauna, such as is characteristic of islands
generally, and indicates that the peninsular nature of the northern
part of the barrier island is of relatively small consequence in
determining presence or absence of species. It is likely that the
restricted environmental spectrum is much more important in this regard
than is the fact of semi-isolation.
Of the 49 species of birds, 10 are known to breed on the island and an
additional 21 are suspected of breeding either on the island or on
small islets in the adjacent Laguna Madre de Tamaulipas. Eleven species
occur on the island as nonbreeding summer residents, about which we
will have more to say below. Four species have been recorded on the
island in summer but breed elsewhere, that is to say, they only wander
over the island (Man-o'-war Bird, Turkey Vulture, _etc._). Two species
are known only as migrants, and the status of one, the Sora Rail, is
uncertain. The number of migrant species doubtless will be greatly
increased by field work at those times when birds migrate.
The avifauna is not depauperate owing to the exclusion of any one of
the three major zoogeographic stocks thought to be important in the
development of the present North American avifauna (Mayr, 1946). If we
examine the breeding passerine birds of the barrier island and the
breeding passerine assemblage at the same latitude in lowland Sonora
(Mayr, _loc. cit._) as to their ultimate evolutionary sources, we find
that for both places somewhat more than half the birds have developed
from indigenous, North American stocks, about one-third have been
derived from South American stocks, and one-fifth to one-eighth are
from Eurasian stocks. It is most unlikely that such close
correspondence in relative composition of the two avifaunas would occur
by chance. Thus, we can only conclude that each of the historical avian
stocks is proportionately restricted in numbers on the barrier island.
Faunistically, the barrier island resembles Padre and Mustang islands
and the adjacent mainland of Tamaulipas and southern Texas, reflecting
the relative uniformity of environment in this region. It is apparent
that there is a faunal "break" or region of transition in the vicinity
of Tampico, in extreme southeastern Tamaulipas. On the coastal plain,
many tropical species and subspecies occurring in Veracruz are found
north to Tampico but fail to extend farther northward to the barrier
island of northeastern Tamaulipas. Axtell and Wasserman (1953:4-5),
have already commented on this situation, mentioning a number of snakes
and lizards that have differentiated subspecifically on opposing sides
of the Tampican region. They also note that large numbers of the
lowland Neotropical floral and faunal elements reach their northern
limits of distribution within the zone of transition around Tampico,
and, also, many Nearctic elements find their southern distributional
limits there.
Our small samples of birds and reptiles from the island show no
detectable morphological differentiation from adjacent populations.
However, several of the mammals are moderately-well differentiated, but
the patterns and degrees of geographic variation are such that we can
only speculate on the historical derivation of the insular populations.
_Lepus californicus curti_ is presently known only from the barrier
island of Tamaulipas, but Hall (1951:43) has suggested that it may also
occur on the adjacent mainland. A resemblance between individuals of
this subspecies and specimens of _L. c. merriami_ from Padre Island in
smallness of the tympanic bullae is regarded, probably correctly, by
Hall (1951:44) as independent development--that is, parallel
adaptation to similar environmental conditions reaching fullest
expression on the barrier island of Tamaulipas. As is also true with
_Geomys personatus_ and _Neotoma micropus_, the barrier island
population of _Lepus californicus_ shows relationships with animals
from Texas and northern Tamaulipas (_L. c. merriami_) and no connection
with (resemblance to) animals from the south (_L. c. altamirae_, known
only from the type locality at Altamira, near Tampico).
In color and cranial proportions, _Dipodomys ordii parvabullatus_ of
the barrier island is closer to _D. o. compactus_ of Padre Island than
to _D. o. sennetti_ of southern Texas and the Tamaulipan mainland. But,
_D. o. parvabullatus_ resembles _D. o. sennetti_ in external
measurements (Hall, 1951:39). Possibly _D. o. parvabullatus_ and _D. o.
compactus_ are phylogentically closer to one another than is either to
_D. o. sennetti_. It is also possible that each evolved independently
from a mainland stock represented today by _D. o. sennetti_; the
resemblance of the two insular populations would thus be a matter of
convergence in response to like environmental conditions.
_Sigmodon hispidus solus_ is an insular differentiate that probably
reached the barrier island from the adjacent mainland of Tamaulipas,
where its apparent closest relative, as judged by morphological
similarity, now occurs.
_Nonbreeding shorebirds in summer south of breeding ranges._--Certain
aspects of this subject have already been discussed by Eisenmann
(1951). As he notes, the phenomenon is more regular and widespread than
generally has been appreciated. The old idea, that such oversummering
individuals were "abnormal" or "senile," is totally inadequate,
especially in view of the frequently large numbers of individuals
involved.
Eisenmann's suggestion that nonbreeders are immature is probably valid,
and it is supported by Pitelka's examination of dowitchers (1950:28,
51). For gulls, which can be aged by characters of plumage, there is no
question that most nonbreeders are immature. Unfortunately, there are
few criteria for determination of age in charadriiform birds.
With the possible exception of a specimen of _Limosa fedoa_, none of
the presumed nonbreeding, oversummering shorebirds collected by us
showed gonadal enlargement above expected minimal sizes for the
species. Even so, the season was late at the time when we were on the
island and most of the birds were molting; it is possible their gonads
had been enlarged earlier in the season. Behle and Selander (1953) and
Johnston (1956) have shown that nonbreeding first-, second-, and
third-year California Gulls (_Larus californicus_) undergo gonadal
enlargement in summer. Additionally, nonbreeding first-year males of
certain passerine species (for example, the Brown Jay, _Psilorhinus
morio_; Selander, 1959) are known to experience partial gonadal
recrudescence in summer. It would be useful, and would facilitate
discussion, to have data on gonadal condition of oversummering birds;
any functional enlargement would be worth documenting.
Some species, notably the Semipalmated Sandpiper, Semipalmated Plover,
and Black Tern, oversummer as nonbreeders in such large numbers that it
is obvious that a significant fraction of the total population of the
species does not breed in any one year. This raises questions
concerning the possible ecologic situations that would select for delay
in time of recruitment of young birds into the breeding segment of the
population, assuming that nonbreeders are immature birds. Delay in
maturation, or slow rates of maturation, may show general relationship
to paucity of sites of breeding, as Orians (1961:308) suggests, but the
shorebirds with which we are dealing breed in regions or in
habitat-types not characteristically imposing general restriction on
sites of nesting; more than one answer is necessary for the question
even at this level. Data on age and numbers of nonbreeders, as well as
on the ecology of breeding populations, are critical and are badly
needed for most species.
In any event, species for which we have data demonstrating that they
regularly oversummer south of their breeding ranges are probably
adapted to having a part of their populations refrain from breeding
each year. Whether this phenomenon can be explained solely in terms of
selection at the level of individual birds (Lack, 1954) or involves
selection of an adaptive response of the population as a whole
(Wynne-Edwards, 1955; see also Taylor, 1961, concerning _Rattus_) is a
problem that cannot be resolved at this time. We may note that the
species involved ordinarily breed in arctic and subarctic regions, and
it would seem advantageous (as set forth below) for nonbreeders to
remain well south of such high latitudes. The numbers of oversummering
individuals may fluctuate with over-all population density, possibly as
a result of crude density, but possibly also as a result of emigration
of individuals in excess of optimal density on breeding grounds (see
Wynne-Edwards, 1959). One aspect of this phenomenon not explicitly
discussed by Wynne-Edwards is the possibility that some individuals
never move north to breeding grounds at all, perhaps as a result of a
behavioral character genetically-grounded and mediated by delayed
maturation of the neurohumoral "clock." This certainly would be an
economical means by which population numbers could be regulated, for
there would be a saving of energy in that some individuals not only
would not move north, but also would not participate in the behavioral
interactions involved in territorial spacing. Occurrence of these birds
throughout southern North America, Middle America, and northern South
America may thus reasonably be understood.
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1952. Mammals of the Tamaulipan Biotic Province in Texas.
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1958. A nesting record of the scissor-tailed flycatcher in
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1960. Late North American spring migrants in Mexico. Auk,
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1951. Checklist of the birds of the central coast of Texas.
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I. Pac. Coast Avif., 29:202 pp.
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1961. The ecology of blackbird (_Agelaius_) social systems.
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1955. The ornithogeography of the Yucatan peninsula. Peabody
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1960. A field guide to the birds of Texas. Houghton Mifflin
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1950. Geographic variation and the species problem in the
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1951. Frigate-bird, oystercatcher, upland plover and various
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1958. Age determination and molt in the boat-tailed grackle.
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1959. Polymorphism in Mexican brown jays. Auk, 76:385-417.
SELANDER, R. K., and ALVAREZ DEL TORO, M.
1955. A new race of booming nighthawk from southern Mexico.
Condor, 57:144-147.
SHANTZ, V. S.
1949. Three new races of badgers (_Taxidea_) from
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1946. Handbook of lizards. Comstock Publ. Co., Ithaca, New
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SUTTON, G. M.
1950. The southern limits of the willet's continental
breeding range. Condor, 52:135-136.
TAYLOR, J. M.
1961. Reproductive biology of the Australian bush rat Rattus
assimilis. Univ. California Publ. Zool., 60:1-66.
THOMPSON, M. C.
1958. Semipalmated sandpiper from Tamaulipas. Wilson Bull.,
70:288.
WYNNE-EDWARDS, V. C.
1955. Low reproductive rates in birds, especially sea-birds.
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behaviour: a hypothesis. Ibis, 101:436-441.
_Transmitted March 15, 1962._
29-3602
UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY
Institutional libraries interested in publications exchange may obtain
this series by addressing the Exchange Librarian, University of Kansas
Library, Lawrence, Kansas. Copies for individuals, persons working in a
particular field of study, may be obtained by addressing instead the
Museum of Natural History, University of Kansas, Lawrence, Kansas.
There is no provision for sale of this series by the University
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individuals request copies from the Museum, 25 cents should be
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for the purpose of defraying the costs of wrapping and mailing.
* An asterisk designates those numbers of which the Museum's supply
(not the Library's supply) is exhausted. Numbers published to date, in
this series, are as follows:
Vol. 1. Nos. 1-26 and index. Pp. 1-638, 1946-1950.
*Vol. 2. (Complete) Mammals of Washington. By Walter W. Dalquest.
Pp. 1-444, 140 figures in text. April 9, 1948.
Vol. 3. *1. The avifauna of Micronesia, its origin, evolution,
and distribution. By Rollin H. Baker, Pp. 1-359, 16
figures in text. June 12, 1951.
*2. A quantitative study of the nocturnal migration of
birds. By George H. Lowery, Jr. Pp. 361-472, 47
figures in text. June 29, 1951.
3. Phylogeny of the waxwings and allied birds. By M.
Dale Arvey. Pp. 473-530, 49 figures in text, 13
tables. October 10, 1951.
4. Birds from the state of Veracruz, Mexico. By George
H. Lowery, Jr., and Walter W. Dalquest. Pp. 531-649,
7 figures in text, 2 tables. October 1, 1951.
Index. Pp. 651-681.
*Vol. 4. (Complete) American weasels. By E. Raymond Hall. Pp. 1-466,
41 plates, 31 figures in text. December 27, 1951.
Vol. 5. Nos. 1-37 and index. Pp. 1-676, 1951-1953.
*Vol. 6. (Complete) Mammals of Utah, _taxonomy and distribution_.
By Stephen D. Durrant. Pp. 1-549, 91 figures in text,
30 tables. August 10, 1952.
Vol. 7. *1. Mammals of Kansas. By E. Lendell Cockrum. Pp. 1-303,
73 figures in text, 37 tables. August 25, 1952.
2. Ecology of the opossum on a natural area in
northeastern Kansas. By Henry S. Fitch and Lewis L.
Sandidge. Pp. 305-338, 5 figures in text. August
24, 1953.
3. The silky pocket mice (Perognathus flavus) of Mexico.
By Rollin H. Baker. Pp. 339-347, 1 figure in text.
February 15, 1954.
4. North American jumping mice (Genus Zapus). By Phillip
H. Krutzsch. Pp. 349-472, 47 figures in text, 4
tables. April 21, 1954.
5. Mammals from Southeastern Alaska. By Rollin H. Baker
and James S. Findley. Pp. 473-477. April 21, 1954.
6. Distribution of Some Nebraskan Mammals. By J. Knox
Jones, Jr. Pp. 479-487. April 21, 1954.
7. Subspeciation in the montane meadow mouse, Microtus
montanus, in Wyoming and Colorado. By Sydney
Anderson. Pp. 489-506, 2 figures in text. July 23,
1954.
8. A new subspecies of bat (Myotis velifer) from
southeastern California and Arizona. By Terry A.
Vaughan. Pp. 507-512. July 23, 1954.
9. Mammals of the San Gabriel mountains of California.
By Terry A. Vaughan. Pp. 513-582, 1 figure in text,
12 tables. November 15, 1954.
10. A new bat (Genus Pipistrellus) from northeastern
Mexico. By Rollin H. Baker. Pp. 583-586. November
15, 1954.
11. A new subspecies of pocket mouse from Kansas. By
E. Raymond Hall. Pp. 587-590. November 15, 1954.
12. Geographic variation in the pocket gopher, Cratogeomys
castanops, in Coahuila, Mexico. By Robert J. Russell
and Rollin H. Baker. Pp. 591-608. March 15, 1955.
13. A new cottontail (Sylvilagus floridanus) from
northeastern Mexico. By Rollin H. Baker. Pp.
609-612. April 8, 1955.
14. Taxonomy and distribution of some American shrews.
By James S. Findley. Pp. 613-618. June 10, 1955.
15. The pigmy woodrat, Neotoma goldmani, its distribution
and systematic position. By Dennis G. Rainey and
Rollin H. Baker. Pp. 619-624, 2 figures in text.
June 10, 1955.
Index. Pp. 625-651.
Vol. 8. Nos. 1-10 and index. Pp. 1-675, 1954-1956.
Vol. 9. 1. Speciation of the wandering shrew. By James S.
Findley. Pp. 1-68, 18 figures in text. December 10,
1955.
2. Additional records and extension of ranges of mammals
from Utah. By Stephen D. Durrant, M. Raymond Lee,
and Richard M. Hansen. Pp. 69-80. December 10, 1955.
3. A new long-eared myotis (Myotis evotis) from
northeastern Mexico. By Rollin H. Baker and Howard
J. Stains. Pp. 81-84. December 10, 1955.
4. Subspeciation in the meadow mouse, Microtus
pennsylvanicus, in Wyoming. By Sydney Anderson.
Pp. 85-104, 2 figures in text. May 10, 1956.
5. The condylarth genus Ellipsodon. By Robert W. Wilson.
Pp. 105-116, 6 figures in text. May 19, 1956.
6. Additional remains of the multituberculate genus
Eucosmodon. By Robert W. Wilson. Pp. 117-123, 10
figures in text. May 19, 1956.
7. Mammals of Coahuila, Mexico. By Rollin H. Baker.
Pp. 125-335, 75 figures in text. June 15, 1956.
8. Comments on the taxonomic status of Apodemus
peninsulae, with description of a new subspecies
from North China. By J. Knox Jones, Jr. Pp. 337-346,
1 figure in text, 1 table. August 15, 1956.
9. Extensions of known ranges of Mexican bats. By
Sydney Anderson. Pp. 347-351. August 15, 1956.
10. A new bat (Genus Leptonycteris) from Coahuila. By
Howard J. Stains. Pp. 353-356. January 21, 1957.
11. A new species of pocket gopher (Genus Pappogeomys)
from Jalisco, Mexico. By Robert J. Russell. Pp.
357-361. January 21, 1957.
12. Geographic variation in the pocket gopher, Thomomys
bottae, in Colorado. By Phillip M. Youngman. Pp.
363-387, 7 figures in text. February 21, 1958.
13. New bog lemming (genus Synaptomys) from Nebraska.
By J. Knox Jones, Jr. Pp. 385-388. May 12, 1958.
14. Pleistocene bats from San Josecito Cave, Nuevo Leon,
Mexico. By J. Knox Jones, Jr. Pp. 389-396. December
19, 1958.
15. New subspecies of the rodent Baiomys from Central
America. By Robert L. Packard. Pp. 397-404. December
19, 1958.
16. Mammals of the Grand Mesa, Colorado. By Sydney
Anderson. Pp. 405-414, 1 figure in text, May 20,
1959.
17. Distribution, variation, and relationships of the
montane vole, Microtus montanus. By Sydney Anderson.
Pp. 415-511, 12 figures in text, 2 tables. August 1,
1959.
18. Conspecificity of two pocket mice, Perognathus
goldmani and P. artus. By E. Raymond Hall and
Marilyn Bailey Ogilvie. Pp. 513-518, 1 map. January
14, 1960.
19. Records of harvest mice, Reithrodontomys, from
Central America, with description of a new subspecies
from Nicaragua. By Sydney Anderson and J. Knox Jones,
Jr. Pp. 519-529. January 14, 1960.
20. Small carnivores from San Josecito Cave (Pleistocene),
Nuevo Leon, Mexico. By E. Raymond Hall. Pp. 531-538,
1 figure in text. January 14, 1960.
21. Pleistocene pocket gophers from San Josecito Cave,
Nuevo Leon, Mexico. By Robert J. Russell. Pp.
539-548, 1 figure in text. January 14, 1960.
22. Review of the insectivores of Korea. By J. Knox
Jones, Jr., and David H. Johnson. Pp. 549-578.
February 23, 1960.
23. Speciation and evolution of the pygmy mice, genus
Baiomys. By Robert L. Packard. Pp. 579-670, 4
plates, 12 figures in text. June 16, 1960.
Index. Pp. 671-690.
Vol. 10. 1. Studies of birds killed in nocturnal migration. By
Harrison B. Tordoff and Robert M. Mengel. Pp. 1-44,
6 figures in text, 2 tables. September 12, 1956.
2. Comparative breeding behavior of Ammospiza caudacuta
and A. maritima. By Glen E. Woolfenden. Pp. 45-75,
6 plates, 1 figure. December 20, 1956.
3. The forest habitat of the University of Kansas
Natural History Reservation. By Henry S. Fitch and
Ronald R. McGregor. Pp. 77-127, 2 plates, 7 figures
in text, 4 tables. December 31, 1956.
4. Aspects of reproduction and development in the
prairie vole (Microtus ochrogaster). By Henry S.
Fitch. Pp. 129-161, 8 figures in text, 4 tables.
December 19, 1957.
5. Birds found on the Arctic slope of northern Alaska.
By James W. Bee. Pp. 163-211, plates 9-10, 1 figure
in text. March 12, 1958.
6. The wood rats of Colorado: distribution and ecology.
By Robert B. Finley, Jr. Pp. 213-552, 34 plates, 8
figures in text, 35 tables. November 7, 1958.