Observations of whooping cranes during winter aerial surveys from 1950 - 2011

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如何引用

研究者應依照以下指示引用此資源。:

Taylor, L. N., Ketzler, L. P., Rousseau, D., Strobel, B. N., Metzger, K., & Butler, M. (2025). (Darwin Core Variant) Observations of Whooping Cranes During Winter Aerial Surveys: 1950–2011 [Data set]. United States Fish and Wildlife Service. https://doi.org/10.7944/SN8J-T710

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此資料的發布者及權利單位為 United States Fish and Wildlife Service。 This work is licensed under a Creative Commons Attribution (CC-BY 4.0) License.

GBIF 註冊

此資源已向GBIF註冊，並指定以下之GBIF UUID: c1a1e3b1-3db5-456d-a961-a31812230f88。  United States Fish and Wildlife Service 發佈此資源，並經由GBIF-US同意向GBIF註冊成為資料發佈者。

關鍵字

Grus americana; Whooping Crane; observations; Occurrence; Observation

聯絡資訊

地理涵蓋範圍

Texas coast, USA (approx. 27.8–28.5° N, 96.5–97.5° W)

分類群涵蓋範圍

Grus americana (Whooping Crane)

時間涵蓋範圍

取樣方法

Caution. These data have quality issues and limitations due to, but not limited to, inconsistencies and lack of documentation on how data were collected, reliance on perceived knowledge of unmarked birds identities, and inaccuracies introduced during both the recording and the digitization step.

方法步驟描述:

1. Steps are taken from the metadata guide published with the original dataset. -Survey Techniques- The intent of the aerial surveys was to obtain a complete count of the Aransas‐Wood Buffalo population on the wintering grounds and estimate recruitment of juveniles into the winter flock (those data are available in Butler et al. 2014a). This survey also resulted in a record of whooping crane locations. Though the survey did not have a formal sampling frame, the observers primarily focused their efforts on areas known to be occupied by wintering whooping cranes (Stehn and Johnson 1987, Stehn and Prieto 2010). As the Aransas‐Wood Buffalo population increased, so did the area they occupied on the wintering grounds, and in turn, the surveyed area. It is unclear what threshold observers used to expand their search area to mirror the extent of the whooping crane population. However, by winter 2010–2011, the surveys were conducted on Blackjack Peninsula, Matagorda Island, Lamar Peninsula, San Jose Island, and Welder Flats. Though more than 44 observers have been involved in the aerial surveys of whooping cranes since winter 1950–1951, the former USFWS Whooping Crane Coordinator, Thomas V. Stehn conducted 2 the surveys for 29 seasons (winter 1982–1983 through winter 2010–2011). The most descriptive summary of the aerial survey techniques can be found in Stehn and Taylor (2008); additional information about the techniques used are available in Butler et al. (2014a, b) and Strobel and Butler (2014). Since no written protocol existed until the whooping crane surveys were revised beginning in winter 2011–2012 (Butler et al. 2014b), there is no way to know how consistent their survey methods or results were from winter to winter. During each winter, survey flights were conducted on multiple days. However, the extent and intensity of the search effort for each flight is unknown since flight paths were not recorded. Surveys spanned up to a 7‐month period each year which included the migratory period. Survey flights began as early as October 9th and ended as late as May 24th. On average, survey flights began on October 22nd (SD = 9.3 days) and ended by April 20th (SD = 16.4 days). Approximately 63% of survey flights were conducted between November 15th and March 31st. Each survey flight consisted of one pilot and at least one observer. The flight paths were typically oriented parallel to the coastline with transects spaced approximately 250–800 m apart in an attempt to cover the entire survey area (Butler et al. 2014b). Transect widths were subjectively determined based on visibility and weather conditions during the survey in an effort to maximize detection of whooping cranes (Butler et al. 2014b). A global positioning system (GPS) device was used beginning in winter 2001–2002 to help maintain parallel transects. However, predetermined flight paths were not used during the aerial surveys nor were flight paths archived. Thus the extent and intensity of search effort for each flight was unknown and likely inconsistent. Surveys were conducted at approximately 60 m above ground level at a speed of approximately 170 km/hr (Stehn and Taylor 2008, Strobel and Butler 2014). Stehn and Taylor (2008) recognized that sun angle and visibility influenced their ability to detect whooping cranes. To address this issue, observers focused their attention to the side of the aircraft opposite of the sun’s position (Stehn and Taylor 2008). However, it is unknown if this practice was implemented prior to winter 1982–1983. Observers attempted to determine the age and group size, and identify any unique individuals (i.e., color‐marked and/or radio‐marked birds) for each whooping crane group they observed. However, if identification was not obtained on the initial pass, the pilot would alter course to allow the observer additional opportunities to confirm data.
2. Steps are taken from the metadata guide published with the original dataset. -Data Recording- Upon observing a whooping crane group, their location was denoted on paper maps by the number of white‐plumaged (i.e., after‐hatch‐year; adult) and tawny‐plumaged (i.e., hatch‐year; juvenile) 3 birds in each group. For example, a group of three birds (2 adults and 1 juvenile) would be denoted as “2+1,” indicating two white‐plumaged birds and one tawny‐plumaged bird were present. These observations were typically written and encircled at their approximate location on a paper map (e.g., Figures 1 and 2). However, some observers marked a dot on the paper map and wrote notes near the dot. In the event that a whooping crane was observed flying, the observer in some cases indicated this on the paper maps as “fly” or as an arrow in the direction it flew. During some surveys, paper maps were used that did not include the entire survey area (i.e., winter 1959–1960 through winter 1962–1963 did not include Matagorda Island). Whooping cranes observed in areas outside the mapped area used for the survey were written along the margin of the map. The types of paper maps varied over the 61 years of the survey (e.g., Figures 1 and 2). Data were recorded on hand‐drawn maps during winter 1950–1951 until winter 1997–1998 (Figure 1). Some hand‐drawn maps had a high degree of landscape detail but most lacked detail. From winter 1998–1999 until winter 2010–2011, observations were recorded on digital orthrophoto quarter quadrangle (DOQQ) maps (Figure 2), although hand‐drawn maps continued to be used for some surveyed areas (e.g., Whitmire Unit, Welder Flats, Lamar Peninsula, Holiday Beach). The scale and resolution of paper maps also varied through time, though the paper DOQQs were approximately 1:46,000.
3. Steps are taken from the metadata guide published with the original dataset. -Uniquely identifiable individuals- Beginning in the late 1970s, the Aransas‐Wood Buffalo population of whooping cranes contained uniquely identifiable marked birds (e.g., color bands). To read the color bands, observers would employ a slow, landing‐type approach (Stehn 1995, Stehn and Johnson 1987). The technique involved the pilot decreasing the altitude of the airplane to approximately 15 m above ground level (Stehn and Taylor 2008). As reported by Stehn, the bands were most often read with the naked eye and, on occasion, with instruments (i.e., binoculars, cameras; Stehn 1995). The color combinations worn by each whooping crane were indicative of the year the bands were placed on the whooping crane (e.g., the nine birds banded in 1977 carried at least one red band; Kuyt 1979). Observers used specific notation to describe and record the identity of color‐marked individuals observed during the aerial surveys. The notation conventions were color‐ and case‐specific. Capital letters represented 80‐mm long bands and lowercase letters represented 40‐mm long bands (Kuyt an Goossen 1987, Stehn 2001). Bands were read left to right leg from top to bottom where a “‐” separates each leg and a “/” separates bands on the same leg. For example, the color combination “G‐w/r” represents a bird with a green, 80‐mm band on its right leg and white, 40‐mm band above a red, 40‐mm band on its left leg. For an individual to be positively identified based on their color band, the use of consistent notation was imperative. For example, “r‐Y” represented a bird banded in 1983, while “R‐Y” represented a bird banded in 1986. Further, some bands were striped (e.g., YbY was a yellow band with a horizontal black stripe; Stehn 2001) or became discolored over time, making positive identification difficult from the aircraft. This resulted in observers using prior knowledge of behavior and presumed territory‐fidelity to confirm color band identification (Stehn 1992, 1995, 2001). These identifications were based on unverified presumptions and, in turn, the validity of these identifications is questionable. Additional information on color‐banded individuals is available as supplementary material to Gil‐Weir et al. (2012) and can be downloaded at onlinelibrary.wiley.com/doi/10.1111/j.1557‐ 9263.2011.00349.x/suppinfo. In addition to color‐marking individuals, 15 hatch‐year birds were equipped with Very High Frequency (VHF) radio transmitters between 1981 and 1983 (Howe 1989, Kuyt 1992, Takekawa and Orthmeyer 2001; Table 1). Those cranes were tracked until their VHF radios were no longer operational. Subsequently, they were identified by their color bands. During aerial surveys, observations of radio‐ and color‐marked individuals were interchangeably recorded as either their VHF radio frequency or color‐band combination.
4. Steps are taken from the metadata guide published with the original dataset. -Digitizing locations of crane observations- To transcribe whooping crane observations into a digital record, technicians visually georeferenced the observations recorded on each paper map using “heads‐up” manual digitizing techniques to approximate the locations of observed birds. They digitized all data using ArcMap 10 by matching the land features in a digital aerial image (2010 images from National Agriculture Imagery Program [NAIP]) as close as possible to the features on the paper maps. Background features (i.e., distinctively shaped ponds, marsh topography) identified both on NAIP images and the paper map were used as spatial references to determine coordinates of each observation. Maps with fewer details (i.e., hand‐drawn maps with coarser scale) were more difficult to identify and match features. Technicians recorded each whooping crane group’s location as the approximate center of each observation marked on the paper maps. The spatial data were projected as North American Datum (NAD) 1983 Universal Transverse Mercator (UTM) Zone 14. Typically the locations of observed whooping cranes were denoted with number(s) that represented the number of individuals observed and enclosed by a circle (see Figures 1 and 2). In the event that a whooping crane flew to a different location (sometimes indicated as “fly” or marked with an arrow in the direction flown), only the original location of the sighting was recorded. In some instances, whooping crane groups were observed but their locations were not record on the paper maps (e.g., no paper maps of the area were available so recorded on the margin of other maps). Observations lacking spatial information were entered as “LOCUNK” in the comments field of the attribute table. When present, additional information provided by the observer such as landcover type and comments was included in supplementary data fields in the attribute table (Table 2). The aircraft type and the names of each pilot and observer were taken from the weekly and annual survey reports (e.g., Stehn 1986, 2001, 2009) and were also entered into the attribute table. The legibility of handwriting varied across observers, survey weather conditions, and survey duration. Therefore, it is likely that misinterpretation caused some error. After the technicians digitized each winter’s data, all data were merged into a single feature class containing an aggregate data table with the coordinates of each location. The attribute table from the feature class was exported as a tab‐delimited text file (i.e., WHCR_Aerial_Observations_1950_2011.txt) which is available for download at http://dx.doi.org/10.7944/W3RP4B.

引用文獻

1. Taylor, L. N., Ketzler, L. P., Rousseau, D., Strobel, B. N., Metzger, K. L., & Butler, M. (2015). Workflow for dataset: Observations of Whooping Cranes During Winter Aerial Surveys: 1950–2011. United States Fish and Wildlife Service. https://doi.org/10.7944/41yd-q805

額外的詮釋資料