Examples of intra- and interspecific re-use of nests abound in the avian world, including eagles enlarging their same nests for many years (e.g. Buehler 2000, Kochert et al. 2002) and owls adopting existing hawk and corvid nests (e.g. Artuso et al. 2014, Bull & Duncan 1993). Several tree-nesting sandpipers – Green Sandpiper Tringa ocropus, Solitary Sandpiper T. solitaria and, to a lesser extent, Wood Sandpiper T. glareola – even re-use old arboreal passerine nests (Oring 1968). In general, however, intra- and interspecific re-use of wader nests by waders appears to be rare, or at least poorly documented, and the few observations thereof have been largely restricted to between seasons (e.g. Cramp & Simmons 1983 [pp. 521, 531, 582], Hansen 2006; but see Table 1 in Kubelka et al. (2014) for a review of interspecific re-use in waders). Such rarity seemingly holds among the tribe Numeniini, as well (e.g. Cramp & Simmons 1983, Dugger & Dugger 2002, Gratto-Trevor 2000, Houston et al. 2011, Marks et al. 2002, McCaffery & Gill 2001). However, both Cramp & Simmons (1983) and Skeel & Mallory (1996) reported rare intraspecific re-use by Whimbrels Numenius phaeopus. Further, Walker et al. (2011) observed both rare between-year re-use by Hudsonian Godwits Limosa haemastica in Alaska, as well as appropriation of a Short-billed Dowitcher Limnodromus griseus nest by godwits in Manitoba. Here I describe the first documented intraseason re-use of a N. phaeopus nest by L. haemastica in North America.
On 22 May 2014, I was visiting areas near the Kanuti River on Kanuti National Wildlife Refuge in north-central Alaska, USA, to resight Whimbrels color-flagged in previous years as part of a five-year breeding ecology study. While in the area, I located a Whimbrel nest (66.15958°N, 151.69716°W) containing one egg. I deemed that the nest had just been initiated based on recent Whimbrel arrival and the phenology of several other nests we had discovered. I flushed the attending bird when I was <50 m from the nest, walked directly to the vacated nest, and recorded its location with a GPS. The attending bird alarm-called regularly while I was near the nest. Its alarm calling attracted its likely mate and a Common Raven Corvus corax which it then attack-mobbed, driving it from its territory. Both Whimbrels of the pair were unflagged.
Two weeks later (4 June) I revisited the general area. Expecting to be mobbed by the aforementioned Whimbrels as I entered their territory, I elicited no such response and suspected that the nest had been abandoned or depredated. I approached the nest to confirm its status and at 4 m from the nest flushed a male Hudsonian Godwit instead. The godwit was silent upon flushing and while it perched atop a nearby tree. The former Whimbrel nest now contained two godwit eggs which I believed to represent an incomplete clutch midway through the egg-laying period, although I did not float the eggs to infer development stage (Liebezeit et al. 2007). I have occasionally observed behavioral dominance by Whimbrels (and never vice versa), suggesting that the Hudsonian Godwits likely appropriated an abandoned or depredated nest, rather than usurped it from actively nesting Whimbrels. Given the Whimbrel nest’s presumed initiation only two weeks earlier, it was too early to have hatched. As the nesting Whimbrels were not flagged, I cannot confirm if they had departed the study area or were re-nesting elsewhere; however, I did not observe any Whimbrels nesting subsequently within this presumed territory.
The godwit nest was empty upon my next visit on 21 June. As its presumed initiation date was about 3 June, I deemed it was too early to have hatched and thus it had been abandoned or depredated or both. However, I cannot definitively rule out hatching, despite its unlikelihood. The estimated combined laying and incubation period for Hudsonian Godwit is 28 days (Walker et al. 2011). Combining this with the unknown failure date for the Whimbrel nest and the similarly unconfirmed development of the godwit eggs, it is possible that the godwit clutch was initiated within a week of 22 May, and that only two eggs had ultimately been laid or there had been partial predation. Nevertheless, I found no evidence of hatching, such as eggshell microfragments (Mabee et al. 2006).
In contrast to some 80 Whimbrel nests found in limited tundra areas near the Kanuti River since 2009, I have located only eight Hudsonian Godwit nests, despite seemingly comparable annual numbers of displaying birds and family groups. With the exception of the nest described here, the microhabitats of these godwit nests have seemingly typified the species, including having considerable overhead cover (Walker et al. 2011); however, the sample size is admittedly small. Godwit nests were all located within then moderately to severely burned inclusions of a 2005 wildfire and typically showed much greater overhead cover (e.g. Labrador tea Ledum decumbens, dwarf birch Betula nana) than the local Whimbrel nests. The re-used nest occurred in a regenerating portion of burned “open low mixed shrub-sedge tussock bog” habitat (Viereck et al. 1992), with three low tussocks Eriophorum vaginatum forming a triangle around the scrape, and 20-cm-high Labrador tea interspersed between them. As has been reported for Whimbrel nests in other areas (e.g. Ballantyne & Nol 2011), overhead cover was largely absent. At Kanuti Lake I have observed Whimbrels and Hudsonian Godwits inhabiting the same tussock bog habitat type, with all located godwit nests occurring within or near presumed Whimbrel nesting territories. While indeed some microhabitat features of their nests seemed to generally differ (e.g. overhead cover), there was nonetheless considerable overlap, including the plant species and microtopography near the nest. The regular use of hummocks or ridges by both species has been documented at Churchill, Manitoba (Skeel & Mallory 1996, Walker et al. 2011). Kubelka et al. (2014) recently summarized general hypotheses for interspecific re-use, including energy savings. Given that Hudsonian Godwits create multiple scrapes during a season (Walker et al. 2011), this hypothesis seems unlikely in the godwit re-use scenario at hand. Kubelka et al. further explored re-use of a Northern Lapwing Vanellus vanellus nest by Little Ringed Plovers Charadrius dubius. While the authors offered interesting behavioral alternatives for re-use in this mixed-size pair (e.g. lapwing nest served as a supernormal stimulus for courting plovers), they pointed out that most re-use is between more similar species, often when breeding closely. Indeed, such may be the case at Kanuti Lake: Whimbrels and Hudsonian Godwits breed in relative proximity there, with enough overlap in nest microhabitat features that occasionally a nest scrape can be “re-used” not because it is a nest per se, but because it simply satisfies the incoming pair’s nest-site selection needs as well.
I gratefully acknowledge A.N. Powell and R.E. Gill, Jr. for their initial reviews of this note. The later reviews of T.G. Gunnarsson and N.R. Senner greatly improved the final manuscript. Lastly, I thank Kanuti National Wildlife Refuge, including my many field assistants who helped locate wader nests, for continued support of Whimbrel and Hudsonian Godwit research.
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