Aves Specta
Explore and Share
Navigation |
The Common Myna at Midway Atoll: Review and Status
Common Mynas have received scant attention since they were first recorded on Midway more than twenty years ago. Concern over this species' deleterious effects on seabirds may lead to consideration of control measures. This BACKGROUND Common Mynas are indigenous to south Asia, but have been introduced to South Africa, Australia, New Zealand, and Pacific islands (Pizzey 1980). They were brought to the main islands of Hawaii in 1865 (Eddinger 1967). Throughout their range mynas are closely associated with human habitation. Because they are adaptable, opportunistic, and do not specialize they often become common enough to be considered a nuisance. An advantageous aspect of myna presence is their appetite for insect pests, but this benefit is tempered on the Leeward Hawaiian Islands by their damage to crops. On islands supporting seabird colonies, mynas are known to prey upon eggs and chicks. Myna predation on Wedge-tailed Shearwater eggs has been documented at Kauai (Byrd 1979) and attacks on nestling and incubating adult White Terns has been observed at Midway (Tyler 1988). Mynas also have been observed pecking open the eggs of Sooty Terns and noddies (Fisher 1948). Return to top BREEDING (From Eddinger's 1967 Oahu study) Nest site selection generally begins in March; both adults build the nest. Eggs are laid one per day until completion of a 2-5 egg clutch. Egg dates occur March through July. Incubation is shared and lasts 13 days (cp. 16-18 days in India). Fledging occurs at age 29-35. Whether more than one successful brood is raised per year is uncertain. During July and August flocks begin to form, and mynas continue to flock through the non-breeding season. Yellow eye skin characteristic of adults begins to show at about 125 days and birds may breed in their first year. Return to top HISTORY OF MYNAS AT MIDWAY I found no record for the introduction of mynas to Midway. Therefore I could not determine whether the pioneers were assisted by humans or if myna presence is the result of natural immigration from the leeward islands. R. L. Pyle (pers. comm., April 1992) recalled rumors of low myna numbers (i.e. 1 or 2 individuals; perhaps up to 5) at Midway in the 1960s. In July 1974, C. P. Sekora searched for and saw 6 mynas (Sincock et al. 1974), for the first USFWS verified record. In their report, Sincock et al. (1974) stated, "presence of the mynah bird at Midway was first reported two years ago." Berger (1981) considered mynas established by 1974, probably based on Sekora's record. The first attempts to quantify the myna population after its expansion were by Byrd (1979, 1980). He estimated 150-200 individuals on Sand Island and none on Eastern. He counted mynas visible along certain streets to provide a population index (Table 1). TABLE 1. Counts of Common Mynas along certain streets on Sand Island. See Appendix for references. Street Decatur Halsey Radford Morrell Commodore Henderson Kramer Bauer Clapp's (1980) reference to Hill Mynahs must be a mistaken reference to Common Mynas. He stated the "population has increased explosively since the summer of 1978." Although he admitted to having "no certain idea" of population size, he considered it "unlikely...the island population is under 250 birds." Following his May visit, Fefer (1982) commented that myna numbers and distribution "seem to be expanding." P. Pyle (1982) estimated 200 mynas during his stay in the autumn of 1982, and recorded a high count of 128 individuals at the landfill dump. In February 1983 Joe Jayasinghe, BSI Wildlife Manager, estimated 600-800 mynas at Midway (Fefer 1983a). Several years passed before the next estimate was made by Tyler (1988); his broad estimate of 750-1500 individuals was made after spending six months at Midway. He is the only observer to have recorded the use of Eastern Island by mynas. McDermond (1989a) noted in the spring of 1989 a "definite increase since September", but I found no record for a September McDermond trip. McDermond (1989b) returned seven months later and remarked that the increase in myna numbers had continued. Neither McDermond (1989b) nor Rowland (1990) saw mynas at Eastern Island, while the latter stated simply that mynas were "common" on Sand Island. The Natural Resources Management Plan for Naval Air Facility Midway Islands Return to top
1992 OBSERVATIONS AT THE LANDFILL It is difficult to obtain an accurate estimate of the population size of Common Mynas at Midway, but opportunities exist to establish population indexes. I used two methods: site counts and transect counts. The landfill dump south of the harbor has a long history of attracting large numbers of foraging and roosting mynas. I estimated myna abundance at the dump on eleven occasions (Table 2). I approached the flocks on foot, pausing frequently to count visible birds. Eventually most of the flock would flush simultaneously, at which time I would estimate abundance by tens before the birds dispersed and landed in trees. In the afternoon of 10 January, I made a ground count followed by a flush estimate and determined that ground counts reveal only about two-thirds of birds present when individuals are scattered across the open area. Also, when mynas are concentrated on dump piles many individuals are hidden. It is likely that most of Midway's mynas can be found at the dump at certain times. When my dump counts were high I found very few mynas over the remainder of the eastern half of Sand Island. Similarly, when I observed widespread dispersal, the dump counts were predictably low. The largest flocks seemed to occur when dump piles contained exposed waste from the galley, whether or not the piles were burning or smoldering, but available material did not guarantee heavy myna use. TABLE 2. Record of myna counts at the landfill dump during DATE 22 Dec 4 Jan 6 Jan 10 Jan 10 Jan 22 Jan 23 Jan 23 Jan 25 Jan 28 Feb 29 Feb * On two occasions I counted mynas flying over the SW corner of the harbor from the direction of the dump. On 4 January between 1710 and 1720 I Return to top 1992 BREEDING ACTIVITY I began to see mynas gathering nest material (cellophane, plastic bags) on 1 March. I monitored one cavity for five weeks beginning 3 March but saw no eggs, despite regularly finding new material on the nest. Air conditioners appear to be favorite nest sites, as do openings on buildings. Old stick nests were found in Area 7 [2006 comment: These stick nests were more likely Brown Noddy than myna]. TRANSECTS Transects were developed at the end of March (Figure 1--not yet online). Transect 1 began at the Fuel Farm gate, proceeded south to the end of Nimitz, Each transect was walked between 0800 and 0900 on the mostly clear and Mynas on the ground and in flight were seen easily. Those perched in TABLE 3. Myna sightings for three transects. Date Transect No. of mynas On ground Perched In flight Heard Total Total 1 + 2 + 3 Pairs Return to top MANAGEMENT The Common Myna is of questionable worth to the avian community at Midway On Oahu, Eddinger (1967:2) remarked, "The myna is a wary bird, and Although elimination of this alien predator of seabird eggs and chicks Natural attrition is difficult to quantify, but some hint may be gleaned TABLE 4. Annual counts of dead mynas picked up by the rat Year 1987 1988 1989 1990 1991 1992 * Through 31 March. When it becomes desirable to remove all or some of the mynas, some Mynas are intelligent, so any control method probably would diminish Return to top ESTIMATE AND SPECULATION I estimate 500 mynas were at Midway this winter, based on general observations made through the period and specific observations of pocket distribution. Repeat counts at the landfill dump probably will provide the most reliable Historical estimates and future impressions of myna abundance should It is obvious the population has undergone rapid expansion during the After such a recent introduction the mynas at Midway offer a wealth of REFERENCES CITED References to Trip Reports are in the Appendix. Berger, A. J. 1981. Common Myna. Pages 202-204 in Hawaiian Birdlife, Byrd, G. V. 1979. Common Myna predation on Wedge-tailed Shearwater eggs. Eddinger, C. R. 1967. A study of the breeding behavior of the mynah (Acridotheres tristis L.). `Elepaio 28:1-5, 11-18. Grant, G. S. 1982. Wildlife on Midway Atoll during the winter and spring Harrison, C. S., M. B. Naughton, and S. I. Fefer. 1984. The status and Pizzey, G. 1980. A field guide to the birds of Australia. Princeton University Press, Princeton, New Jersey. Stone, C. P. 1989. Non-native land vertebrates. In C. P. Stone Tyler, W. B. 1988. Trip report. Unpublished report, U.S. Fish and Wildlife APPENDIX USFWS trip report authors, year and dates of trips. All reports found TRIP REPORTS FOR MIDWAY ONLY
TRIP REPORTS FOR MIDWAY VISIT COMBINED WITH OTHER ISLANDS
Midway trip reports not found in FWS Honolulu or Midway files
Submitted to the refuge biologist at Midway Atoll NWR in October 1992. Revised and posted to http://www.halcyon.com/salix/myna.htm in February Latest revision: March 1997, with comments added 2006. Return to top. Further Developments The gonadal cycle is controlled by daylength and humidity. http://www.swets.nl/sps/journals/brr2702.html#anchor555558 Paul and Helen Baker estimate population at 800 in February 1996, but I doubt it. |
Wells Reserve Blog |
Post new comment