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Hatching chronology of ducks using playas in the southern high plains of Texas.

INTRODUCTION

Studies of breeding ducks in the Southern High Plains (SHP) have focused on documenting abundance, species composition and production (Traweek, 1978; Rhodes and Garcia, 1981; Berthelsen et al., 1989; Ray et al., 2003). Ray et al. (2003) documented 47 breeding pairs per 100 [km.sup.2] and Traweek (1978) calculated annual brood densities ranging from 18-52 broods per 100 [km.sup.2]. The most common habitat used by breeding pairs is playas (Ray et al., 2003), and Mallards tend to be the most common breeding ducks. Mallards represented 29-43% of adults observed by Traweek (1978), 54-66% of the breeding pairs observed by Ray et al. (2003) and 61-81% of broods observed by Traweek (1978). Breeding pairs of Blue-winged Teal (Anas discors), Cinnamon Teal (A. cyanoptera), Gadwall (A. strepera), Northern Pintail (A. acuta), Northern Shoveler (A. clypeata), Redheads (Aythya americana) and Ruddy Ducks (Oxyurajamaicensis) also occur during spring and summer (Traweek, 1978; Ray et al., 2003).

We contributed information on brood abundance in playas and provided the first information pertaining to hatching chronology in the SHP. Hatching chronology of ducks has not been documented for this region. Because of the regions importance as a production area in many years, knowledge of hatching chronology can be used to make recommendations regarding production surveys (Naugle et al., 2000) and timing of haying and grazing in nesting areas (Dale et al., 1997; McMaster et al., 2005). Our goal was to help habitat managers avoid manipulation of nesting habitats during critical periods and to identify dates best suited for brood surveys.

STUDY AREA

Playas were surveyed in a six county area in the SHP of Texas. Playas comprised about 2.6% of the land area in these counties (Fish et al., 2000). They are the dominant wetland feature in both the counties and the region (Smith, 2003); approximately 3604 playas occur in the six counties and about 19,340 occur in the Texas portion of the SHP (Bolen et al., 1989a, b; Fish et al., 1999). Playas in the six counties averaged 10.9 ha (Fish et al., 1999), which is larger than the average size of 6.3 ha typically referenced for playas (Guthery and Bryant, 1982; Bolen et al., 1989b). Elevation of the eastern most survey playa was 1023 m and elevation of the western most playa was 1250 m.

Playas are shallow, often circular basins that have closed watersheds; they experience largely unpredictable wet/dry cycles (Guthery and Bryant, 1982; Bolen et al., 1989b). They fill intermittently by intense isolated thunderstorms, although some receive water from municipal or agricultural related runoff (Bolen et al., 1989b; Haukos and Smith, 2004). Rainfall in the SHP averages 33-45 cm annually and typically occurs during Apr.-Jun. and Sep.-Oct. (Bolen et al., 1989b).

Playas are the primary wetland habitats used by most breeding, migrating and wintering waterfowl in the SHP (Bolen et al., 1989a; Smith, 2003). Playas also host Sandhill Cranes (Grus canadensis), breeding and migrant shorebirds, and other wildlife (Smith, 2003). Upland habitats include irrigated and non-irrigated agricultural lands (cotton, corn, sorghum and winter wheat), shortgrass prairie, and formerly tilled lands now enrolled in the Conservation Reserve Program (i.e., planted back to native or non-native grasses; Haukos and Smith, 1994).

METHODS

Brood surveys were conducted along four survey routes spanning six counties that were established for a study of waterfowl migration chronology on playas (see Baar et al., 2008). Routes were established because of their proximity and juxtaposition to wet playas and varied in length. Ali playas along routes could be viewed from roads with either binoculars or a spotting scope. We assumed that visibility biases related to distance of playas from the road did not affect results related to hatching chronology, so we did not make attempts to correct for distance. At the start of surveys in 2005 the routes included 5-12 wet playas each for a total of 36 wet playas (Fig. 1). In 2006, no brood surveys were conducted due to severe drought and a lack of wet playas. In 2007, only two of the routes were surveyed, as the other two did not have wet playas. These two routes contained eight and 11 playas each; one of them (eastern most route) was modified to include four wet playas that were not included in Baar et al. (2008). Although one playa was noted receiving periodic runoff from crop irrigation and one from a confined animal feeding operation, no routes included playas that were permanent due to inflows from agriculture or municipal runoff. Playas were not surveyed when they were dry.

Playas were surveyed for broods once every 2 wk from Apr.-Sep. in 2005 and 2007. Surveys started at sunrise and generally ended around noon. Data recorded for each brood observed included species, brood size and age class (Gollop and Marshall, 1954). The Gollop and Marshall (1954) aging technique is based on plumage development and uses seven age subclasses. Broods of Cinnamon Teal and Blue-winged Teal were combined because it was difficult to consistently differentiate them (Bellrose, 1980; Rhodes and Garcia, 1981). All brood surveys were performed by the authors.

After each brood's age class was determined, the mid-point of that age class, which varies by species, was subtracted from the Julian Date of the brood observation to approximate hatch date (Gollop and Marshall, 1954; Naugle et al., 2000). For example, the mid-point in age for a Stage lb Mallard brood is 10 d, so if observed on Julian Date 167 its approximate hatch date would be Julian Date 158. Hatch date was not adjusted for brood size because all eggs within a nest hatch synchronously (Afton and Paulus, 1992). If a brood was observed with an approximate hatch date that was similar ([+ or -] 4 d) to a hatch date for a previous brood on the same playa, then the later brood was excluded (Naugle et al., 2000). Because many of the playas went dry during summer, and because all playas on certain routes went dry, no attempts were made to test for playa, route or year-to-year differences in hatching chronology.

To calculate the period of time that each brood was potentially present on a playa, we added the species specific prefledging period (time from hatch to flight) to the approximate hatch date of each brood (Naugle et al., 2000). We then summed broods across playas to obtain total brood abundance by survey period. Prefledging periods are from Bellrose (1980).

RESULTS

After filtering data for broods likely counted more than once, we observed 69 broods on 36 playas in 2005 and 61 broods on 19 playas in 2007. Broods were found on 67% and 79% of wet playas in 2005 and 2007, respectively. Mallards accounted for most observations, followed by Blue-winged Teal and Cinnamon Teal. Broods of Northern Pintail, Gadwall and Northern Shoveler also were observed (Fig. 2). Broods per playa averaged 1.9 ([+ or -] 0.4 SE, range 0-12) in 2005 and 3.2 ([+ or -] 1.0 SE, range 0-19) in 2007.

The period between the first and last brood hatched was 119 d in 2005 and 114 d in 2007. Mallards tended to hatch earlier than other species; the first Mallards hatched [greater than or equal to] 50 d before Blue- winged Teal and Cinnamon Teal in both years (Fig. 2). An estimated 27% of all broods observed hatched during 1-15 Jun., which was the peak period of hatch (Table 1). By 15 Jul., 90% of all broods, including 97% of Mallards and 75% of Blue-winged Teal and Cinnamon Teal, had hatched (Table 1). Brood abundance, in terms of percent of total broods occurring on playas in any period, peaked during the Jul. periods (Table 2).

DISCUSSION

Mallards in this study started hatching a month earlier than Mallards in North and South Dakota (Duebbert and Frank, 1984). However, as in the Dakotas, Mallards in our study nested early relative to other species (Sowls, 1955; Duebbert and Frank, 1984); almost all (97%) Mallards hatched before 15 Jul. Likewise, the late appearance of Blue-winged Teal and Cinnamon Teal broods suggested they follow a pattern similar to those that breed in more northerly areas (Sowls, 1955; Duebbert and Frank, 1984; Gammonley, 1996).

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Smith (2003) suggested that the relatively long breeding period in the SHP would make brood surveys problematic and, moreover, would cause production estimates to be underestimated. Smith (2003) noted that Class 1 ducklings (Gollop and Marshall, 1954) were observed on playas from Apr. through Sep. We observed Class 1 ducklings from early Apr. (Class 1a) through the 3rd wk of Aug. (Class 1c). Brood abundance peaked during Jul. survey periods. Surveys during this time should capture >70% of broods that occur annually on playas, which is comparable to production surveys in portions of the Prairie Pothole Region (Naugle et al., 2000). As predicted by Smith (2003), production is underestimated. It is possible that the percentage of broods captured might be <70% for surveys applied across the entire SHP.

Nesting habitat of dabbling ducks (Anas spp.) in the SHP is not well documented. It is probable, however, that they use habitats comparable to those used by Ring-necked Pheasants (Phasianus colchicus) that nest in the region, such as shortgrass prairie, Conservation Reserve Program land, winter wheat, road right-of-ways and playa margins (Guthery et al., 1984; Berthelsen et al., 1989). Haying, mowing and other such manipulations of these habitats should be delayed until 15 Jul. or later. This will give >90% of duck broods a chance to reach playas.

The species composition of dabbling duck broods we observed was similar to earlier studies (Traweek, 1978; Rhodes and Garcia, 1981). We observed no diving duck (Aythya spp. or Ruddy Duck) broods, however. Traweek (1978) detected diving duck broods in all 4 y of his study. We observed adult Redheads and Ruddy Ducks in both years and quantified their numbers in 2005; Redheads averaged 0.6 ([+ or -] 0.2 SE) adults per playa across survey periods and Ruddy Ducks averaged 1.2 ([+ or -] 0.4 SE). It is possible broods were missed, but the SHP may be less attractive now to over-water nesting ducks than during Traweek's (1978) study. Irrigation runoff has declined and, subsequently, there may be less emergent vegetation (Smith, 2003).

Acknowledgments.--This work was supported by Texas Parks and Wildlife through sales of state waterfowl stamps and through Federal Aid in Wildlife Restoration Act Project W-128-R, the Playa Lakes Joint Venture through contributions by ConocoPhillips, and the Killgore Research Center at West Texas A&M University. R. T. Kazmaier provided valuable assistance with many aspects of the study. The authors thank G. T. Miller, J. D. Ray and J. A. Roberson for reviewing the manuscript.

Submitted 4 August 2008; accepted 27 February 2009.

LITERATURE CITED

AFTON, A. D. AND S. L. PAULUS. 1992. Incubation and brood care, p. 62-108. In: B. D.J. Batt, A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson, J. A. Kadlec and G. L. Krapu (eds.). Ecology and management of breeding waterfowl. University of Minnesota Press, Minneapolis. 635 p.

BAAR, L., R. S. MATLACK, W. P. JOHNSON AND R. B. BARRON. 2008. Migration chronology of waterfowl in the Southern High Plains of Texas. Waterbirds, 31:394-401.

BELLROSE, F. C. 1980. Ducks, geese, and swans of North America. Stackpole Books, Harrisburg, Pennsylvania. 540 p.

BERTHELSEN, P. S., L. M. SMITH AND C. L. COWMAN. 1989. CRP land and game bird production in the Texas High Plains. J. Soil Water Conserv., 44:504-507.

BOLEN, E. G., G. A. BALDASSARRE AND F. S. GUTHERY. 1989a. Playa lakes, p. 341-365. In: L. M. Smith, R. L. Pederson and R. M. Kaminski (eds.). Habitat management for migrating and wintering waterfowl in North America. Texas Tech University Press, Lubbock. 560 p.

--, L. M. SMITH AND H. L. SCHAMM, JR. 1989b. Playa lakes: prairie wetlands of the Southern High Plains. BioScience, 39:615-623.

DALE, B. C., P. A. MARTIN AND P. S. TAYLOR. 1997. Effects of hay management on grassland songbirds in Saskatchewan. Wildl. Soc. Bull., 25:616-626.

DUEBBERT, H. F. AND A. M. FRANK. 1984. Value of prairie wetlands to duck broods. Wildl. Soc. Bull., 12:27-34.

FISH, E. B., E. L. ATKINSON, T. R. MOLLHAGEN, C. H. SHANKS AND C. M. BRENTON. 2000. Playa lakes digital database for the Texas portion of the Playa Lakes Joint Venture region. Texas Tech University, College of Agricultural Sciences and Natural Resources, Unpublished Report (Summary statistics for Technical Publication T-9-813), Lubbock. 37. http://www.rw.ttu.edu/gstlab/playas.pdf. (Feb. 2009)

--,--, C. H. SHANKS, C. M. BRENTON AND T. R. MOLLHAGEN. 1999. Playa lakes digital database for the Texas portion of the Playa Lakes Joint Venture region. Texas Tech University, College of Agricultural Sciences and Natural Resources, Technical Publication T-9-813 (CD-ROM), Lubbock.

GAMMONLEY, J. H. 1996. Cinnamon Teal (Arias cyanoptera). In: A. Poole and F. Gill (eds.). The birds of North America, No. 209. Academy of Natural Sciences, Philadelphia, Pennsylvania, and American Ornithologists' Union, Washington, D.C. 20 p.

GOLLOP, J. B. AND W. H. MARSHALL. 1954. A guide for aging duck broods in the field. Mississippi Flyway Technical Section, 14 p. http://www.npwrc.usgs.gov/resource/birds/ageduck/index.htm (Feb. 2009).

GUTHERY, F. S. AND F. C. BRYANT. 1982. Status of playas of the Southern Great Plains. Wildl. Soc. Bull., 10:309-317.

--, R. W. WHITESIDE, T. T. TAYLOR AND T. SHUPE. 1984. How to manage pheasants in the Southern High Plains of Texas. Texas Tech University, Range and Wildlife Management, Management Note 3, Lubbock. 6 p.

HAUKOS, D. A. AND L. M. SMITH. 1994. The importance of playa wetlands to biodiversity of the Southern High Plains. Landscape Urban Planning, 28:83-98.

--AND--. 2004. Plant communities of playa wetlands in the Southern Great Plains. Museum of Texas Tech University, Special Publications, No. 47, Lubbock. 63 p.

MCMASTER, D. G., J. H. DEVRIES AND S. K. DAVIS. 2005. Grassland bird nesting in haylands of southern Saskatchewan: landscape influences and conservation priorities. J. Wildl. Manage., 69:211-221.

NAUGLE, D. E., R. R. JOHNSON, T. R. COOPER, M. W. HOLLAND AND K. F. HIGGINS. 2000. Temporal distribution of waterfowl surveys in eastern South Dakota: implications for aerial surveys. Wetlands, 20:177-183.

RAY, J. D., B. D. SULLIVAN AND H. W. MILLER. 2003. Breeding ducks and their habitats in the High Plains of Texas. Southwest. Nat., 48:241-348.

RHODES, M. J. AND J. D. GARCIA. 1981. Characteristics of playa lakes related to summer waterfowl use. Southwest. Nat., 26:231-235.

SMITH, L. M. 2003. Playas of the Great Plains. University of Texas Press, Austin. 257 p.

SOWLS, L. K. 1955. Prairie ducks: a study of their behavior, ecology and management. Stackpole Company, Harrisburg, Pennsylvania. 193 p.

TRAWEEK, M. S, JR. 1978. Waterfowl production survey. Texas Parks and Wildlife Department, Federal Aid Project Report Number W106-R-5, Austin. 17 p.

WILLIAM P. JOHNSON, (1) Texas Parks and Wildlife Department, P.O. Box 659, Canyon 79015; LAURA BAAR, (2) RAYMOND S. MATLACK AND RAYMOND B. BARRON, Department of Life, Earth and Environmental Sciences, West Texas A&M University, Box 60808, Canyon 79016.

(1) Corresponding author: e-mail: bill.johnson@tpwd.state.tx.us

(2) Current address: Texas Parks and Wildlife Department, P.O. Box 226, Karnack 75661
TABLE 1.--Frequency of hatches within 2 wk periods for broods
observed on playas in the Southern High Plains of Texas during
2005 and 2007

Period      2005   2007   Combined   Cumulative percentage

1-15 Apr      1      1        2               1.5
16-30 Apr     2      2        4               4.6
1-15 May     14      4       18              18.5
16-31 May    13     12       25              37.7
1-15 Jun     18     17       35              64.6
16-30 Jun     8     10       18              78.5
1-15 Jul      7      8       15              90.0
16-31 Jul     4      7       11              98.5
1-15 Aug      2               2             100.0

Taste 2.--Low and high estimates of brood abundance on playas during
2 wk periods in the Southern High Plains in 2005 and 2007 (years
combined). The low estimate is the percent of broods present during
the entire 2 wk period (total number present at least 1 d during
period minus those that either fledged or hatched dining period /
total number of broods observed in study) and the high estimate is
the percent of broods present for at least 1 d of the period (total
number present at least 1 d during period /total number of broods
observed in study)

                Percent

Period      Low    High

1-15 Apr.    0      1.5
16-30 Apr.   1.5    4.6
1-15 May     4.6   18.5
16-31 May   18.5   37.7
1-15 Jun.   43.8   63.9
16-30 Jun.  60.0   74.6
1-15 Jul.   71.5   83.1
16-31 Jul.  72.3   79.2
1-15 Aug.   50.8   52.3
16-31 Aug.  12.3   30.8
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Title Annotation:Notes and Discussion
Publication:The American Midland Naturalist
Article Type:Report
Date:Jan 1, 2010
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