On 8 July 2014 I was part of a crew conducting surveys for Dakota Skipper (Hesperia dacotae) in southeastern Estevan County, Saskatchewan. The weather was warm with a mix of sun and cloud and a steady breeze. We passed through a multi-year fallow area of reasonably tall grass prairie that appeared to have a seep or spring widely pooling (or draining) below the vegetation. The northwest corner of the tall grass plot appeared to hold more water than the rest of the feature and contained several singing Sedge Wren. The remaining 90% of the tall grass habitat had an unusual abundance of singing Grasshopper Sparrow. It was unlike other habitats or avian communities visited by the authors during our fieldwork in the region. Around 2 pm I first heard a short insect like song of a Henslow’s Sparrow (HESP) and paused to listen. After several minutes I was reasonably confident I had heard a second clear yet short HESP song. We paused to confirm that we were outside the known range of the species. After waiting several more minutes, a single, poorly defined and unconfirmed song was detected. My unfamiliarity with all aspects of the local fauna and their noises, time of day, brevity of calls, range disparity and a pressing work schedule led us to dismiss the short calls and we traveled to our next survey site.
Several hours passed completing additional surveys and we traveled back to a rental cottage for the evening. A query of the eBird database showed numerous records in Minnesota with sporadic occurrences in North and South Dakota but no records from the Canadian prairies. Further reading was focused on the HESP’s preferred habitat requirements, listed in the Canadian Recovery Strategy as tall and dense grass cover, a thick thatch layer, a lack of emergent vegetation, large areas of grassland habitat and low-lying wet area. Many of these features were matched by the habitat visited earlier in the day where the potential HESP songs had been heard.
We therefore decided to drive back to the site in an attempt to confirm the observation, arriving after dusk with a portable speaker in tow. The wind had dropped and the skies were clear, with a large moon rising above the horizon. Grasshopper Sparrows were the only birds vocalizing; short insect like buzzes, unlike their primary song. After a few minutes of silent listening and no results, playback was initiated. The recording was repeated ~40 times without response. The author ceased playback and began preparation to leave the site when a loud and clear song of the HESP was clearly heard. It was so prominent that I assumed it had come from the speaker. Playback was initiated again with six or seven additional songs but none received a response. It wasn’t until playback had been stopped that the loud clear song of a HESP was heard once again at very close range. Over the next several minutes brief 2-3 plays of the digital song were used to elicit a response from the inquisitive male HESP. The light was not suitable for photographs, so recordings of the song were made with “video mode” on a point and shoot camera (Canon Powershot SX30). After securing audio documentation we left the site.
The following day called for surveys well away from the HESP location, meaning any follow-up observations were not possible. Due to the nature of the surveys and the observation occurring on private property, permission to immediately release the sighting was not granted. A digital recording of the song is available on eBird and two sonograms were produced.
Habitat Notes:
The habitat was that of multi-year fallow tallgrass prairie, notable in having very shallow pools of water beneath the thatch layer. Using google earth, the core habitat was measured as roughly 500 m east/west by 200 m north/south, roughly 10ha, with a sparse border of deciduous shrubs and trees. Within the core habitat, the northwestern corner appeared to be the water outflow source, suspected of being a seep or spring. The ground in this area was uneven with scattered tussock features. The remainder of the core habitat (90%) was the level tallgrass prairie with ubiquitous shallow pools underneath the thatch layer. Similar habitat was likely present ~200 m beyond the western and eastern limits of the core habitat although it was not visited by the authors. On the northern edge, dry level prairie extended several hundred meters beyond a slight treed ridge. To the south, dry short-grass prairie hills containing the target species of Dakota Skipper such as Purple Coneflower and Porcupine Grass stretched for ~100 m before levelling off over a broad floodplain. Measuring all immediate prairie habitats yields an area of 30 ha, with an extended area of 150 ha before prairie or grassland habitats are no longer the dominant vegetation community. Due to the nature of the observation, an inventory of plant species was not completed. Four photographs were taken, facing N, E, S and W; from the centre of the core habitat (see slideshow below).
This singing male from Estevan County, responding to playback in damp tallgrass prairie, likely represented a territorial individual. The Canadian recovery strategy suggests that wetter sites may be the historical preferred breeding habitat it would be “the most stable vegetation structure from year to year” and it has been reported that HESPs are more abundant at specific sites in Illinois during years with increased moisture conditions. Due to the nature of this observation, there are many questions left unanswered surrounding potential breeding or site fidelity. It is hoped that the details in this account can provide insight for those working to identify additional occurrences of this rare species.