Dayson Basin – 15 May 2017

On Monday, 15 May 2017 a group of 3 birders visited the U.S. Marine Corps Support Facility – Blount Island, Dayson Basin, where we drove the length of the 2.5 mile elevated berm around the property. We made four stops for stationary observations. The basin was very dry and the western side of the property was devoid of any standing water. The eastern side of the basin still had a large shallow pond of water but still had very low numbers of shorebirds and waders; this may be in part due to low tide in the surrounding marshes, as many shorebirds likely spend time foraging on the exposed mudflats during low tide.

This past weekend visits to Big Talbot Island State Park’s “Spoonbill Pond” yielded similar low numbers, as did Huguenot Memorial Park. The new Army Corps of Engineers mitigation area off Heritage River Road about 1.5 miles from Dayson Basin had larger numbers and greater diversity in shorebird species during a morning visit on 14 May; that visit coincided with high tide thus numbers of birds were driven there.

This morning’s visit only lasted about 1.5 hours since the birds were concentrated in essentially one location. Forty-five (45) species were recorded, including 10 species of shorebird. Species observed that are known to breed locally and appear to be in suitable habitat on the property include Mottled Duck, Green Heron, Osprey, Clapper Rail, Black-necked Stilt, Wilson’s Plover, Killdeer, Least Tern, Gull-billed Tern, Common Ground-Dove, Mourning Dove, Downy Woodpecker, Great Crested Flycatcher, White-eyed Vireo, Blue Jay, Fish Crow, Carolina Chickadee, Carolina Wren, Eastern Bluebird, Northern Parula, Northern Cardinal, and Painted Bunting. The group confirmed an occupied Osprey nest, a probable nest site for Wilson’s Plover, and several singing songbirds (including Painted Bunting) that would suggest nesting.

We observed just one waterfowl species: Mottled Duck.

Notable shorebird species included 4 Stilt Sandpipers, 2 Wilson’s Plovers, 4 Black-necked Stilts, and 6 White-rumped Sandpipers.

Stilt Sandpipers continue in the basin.

As noted during our last visit, Stilt Sandpipers winter in central South America and breed in the low arctic tundra; they are very uncommon in NE FL where small groups are usually found at Big Talbot Island State Park’s Spoonbill Pond in migration. This spring, there has been only one report of a single Stilt Sandpiper from Spoonbill Pond; all other reports have come on the two visits to the Basin. White-rumped Sandpiper is another long distance migrant and they usually pass through beginning around May 1st in very low numbers.

The group recorded three Gull-billed Terns in the middle of the eastern end. Gull-billed Terns breed locally and have been in a steep decline the last ten years due to habitat loss. To see three together in Jacksonville in recent years is a true rarity.

Gull-billed Terns.

White-rumped Sandpipers

I have White-rumped Sandpipers flagged as “rare” in eBird in the counties I review because they’re a scarce migrant that is often mis-identified. I cringe every time I get a report that relies most heavily on “I saw the white rump in flight”. Not to say that you can’t see the rump on a bird in flight, but it’s very difficult to see it unless you’re close, the bird isn’t  flying erratically (Iike small shorebirds tend to do), you have excellent optics, great light, and hell – just a keen eye. I’ve seen many hundreds of White-rumped Sandpipers and I can’t honestly remember a time that I identified one in flight. That isn’t to say it can’t be done, but it’s tricky and there are much better ways to identify this species.

This year, I’ve gotten a little better with my photography skills and have taken a million pictures of White-rumped Sandpipers that I’ve found in three locations in Duval County thus far (Spoonbill Pond, Haulover Creek, and Heritage River Road Wetlands). I hope that these pictures and explanations are helpful study guides for anyone struggling with identifying these birds in the field.

Tip 1: I start looking for White-rumped Sandpipers in northeast Florida after the first of May, and then by scanning flocks of shorebirds in shallow pools and mudflats. This could mean inland puddles in flooded fields or pastures, places like Spoonbill Pond, or tidal marshes with exposed mud. A quick scan of a flock of small birds should tell you right away if a White-rumped is present, because they are significantly, noticeably larger than Least and Semipalmated/Western Sandpipers. Figure 1 below may be a typical binocular view of such a flock; you can see how easily the larger White-rumped stands out from the Semipalmated and Least Sandpipers.

Fig. 1. Standing out in a crowd.

Figure 2 below shows the significant size difference between a White-rumped and Least Sandpiper.

Fig. 2. Size comparison of White-rumped and Least Sandpipers.

Tip 2: Look for the reddish area at the base of the lower mandible. This is actually easier to see than it sounds. Figures 3 and 4 illustrate just how easily that field mark stands out.

Fig. 3 – Red displaying at base of lower mandible
Fig 4. Red mandible and classic profile.

Tip 3: The classic profile. To me, White-rumped Sandpipers have a classic profile that is often described as “long”, “lean”, or “attenuated”. Figure 4 above illustrates this look to a tee. In that image, not only can you see the red area at the base of the mandible but you can see that tapered look where the strong muscular back dips to a narrow point around the rump before flaring out through the length of those long primaries. The primaries and tail often present a “scissored” look like you see in Fig 4. Another view you may see is from the front or rear of the bird, where the “scissored” effect is even more dramatic, as in Fig. 5. This bird was photographed in May 2016 at Westside Industrial Park and you can clearly see how the primaries are so long that they cross in the back. When you see this, you have one of two things here: White-rumped or the incredibly more rare Baird’s.

Fig 5. Scissored primaries. White-rumped Sandpipers (left and right) with Least Sandpiper (middle).

Tip 4: The supercilium. The White-rumped Sandpiper will display a white supercilium in all ages and plumages. Figure 4 demonstrates this as does Figure 6, where you can’t even see most of the bird’s face and none of the bill.

Fig. 6. The strong, bold supercilium stands out.

Tip 5: The rump. The most common eBird comment made when writing up this species is something about “seeing the white rump in flight”. It should be noted that Western, Least, and Semipalmated Sandpipers all also have white in the rump, as do Sanderlings, Pectorals, Dunlin, and Stilt Sandpipers! What I don’t recall ever seeing is anyone extending their comment to specify the White-rumped Sandpiper has a solid, unbroken band of white in sort of a horseshoe shape (Fig. 7) and stating that the bird they saw had this trait and not a broken pattern divided by a dark central point like some of the other species mentioned would exhibit. I can’t stress this enough: use caution when relying on seeing a flash of white in the tail or rump of a shorebird to ID it to species.

Fig. 7. The “white horseshoe”.