The Spotted Sandpiper (Actitis macularius) is a small shorebird that breeds across most of Canada and the northern United States. It is a distinctive bird with some unique behaviors and adaptations that set it apart from other sandpipers. In this article, we will explore what makes the Spotted Sandpiper special.
Description and Range
The Spotted Sandpiper is a small-medium sized sandpiper, measuring around 6.3-7.5 inches in length with a wingspan of 11-13 inches. Adults have grayish-brown upperparts with white underparts. True to their name, they have bold round black spots on their white chest and belly. Their most distinctive feature is their teetering motion when they walk, continuously bobbing their backside up and down.
Range | The Spotted Sandpiper has an extremely large range, breeding throughout most of Canada and Alaska, across the northern United States, and south along the Pacific coast. Its winter range stretches from the southern half of the U.S. south to Panama and the Caribbean. |
---|---|
Habitat | During breeding season, Spotted Sandpipers live along the edges of freshwater wetlands, ponds, streams, and rivers. They can also be found in human-created habitats like reservoir shorelines and sewage treatment plants. In migration and winter they occur along both freshwater and coastal habitats. |
Diet | Spotted Sandpipers forage by scanning for prey while walking along the shoreline or wading in shallow water. They mainly eat small invertebrates like insects, crustaceans, mollusks, and worms. They will also consume tadpoles and small fish. |
Unique Behaviors
The Spotted Sandpiper exhibits some interesting behaviors that set it apart from other sandpipers:
Teetering Motion
As mentioned above, Spotted Sandpipers continually bob their hindquarters up and down as they walk. This distinctive teetering motion helps them stir up insects and makes them more conspicuous. The teetering may also help flush out prey items hidden in mud or vegetation.
Solitary Nesting
Most shorebirds nest in colonies, but the Spotted Sandpiper nests solitarily. This likely helps reduce competition for the insects and other prey their chicks rely on.
Polyandry
Spotted Sandpiper females are polyandrous, meaning they mate with multiple males over the course of the breeding season. The female lays between four to five eggs which are each fertilized by a different male. She then abandons the male to provide all parental care while she goes off to mate with other males.
Role Reversal
Due to their polyandrous mating, Spotted Sandpipers exhibit a complete reversal of typical shorebird gender roles. Males arrive first at the breeding grounds and establish a territory. When females arrive, the males display to attract a mate. After copulating, the female lays a clutch of eggs that the male then incubates alone. The female provides no care and may mate with additional males, laying clutches in up to four different nests.
Meanwhile, the male incubates the eggs for around 20-27 days until they hatch. The hatchlings are covered in downy cryptic feathers and leave the nest within hours. The male takes sole responsibility for defending the chicks’ territory, brooding them at night, and feeding them for their entire 28-34 day fledging period.
This unique role reversal, where males provide all parental care, allows females to lay more clutches and produce more offspring per season than if they cared for their own young.
Migration
The Spotted Sandpiper undertakes an extensive migration each year. They breed across northern North America in the summer months. By late July, adults begin departing the breeding grounds, followed by juveniles in late August and September. They migrate south on a broad front to their wintering grounds in the southern U.S., Mexico, Caribbean, and South America.
Northward migration occurs on a similar broad front from March to May. One of the last shorebirds to arrive on the breeding grounds, they time their arrival to coincide with the emergence of caterpillars and other insects to feed their young. It is estimated Spotted Sandpipers may migrate over 9,300 miles round trip each year.
Population and Conservation
Spotted Sandpipers remain a common and widespread species. Partners in Flight estimates a global breeding population of 3.5 million with 43% spending some part of the year in the U.S. They are a Species of Least Concern according to the IUCN. Their populations face no major threats. As habitat generalists that utilize both natural and human-altered shorelines, they are adaptable to some level of habitat modification across their range.
Fun Facts
Here are a few fun and interesting facts about the unique Spotted Sandpiper:
- Spotted Sandpiper chicks feed themselves from hatching. Like tiny precocial adults, they chase down insects on their own.
- To warn chicks of danger, the father Spotted Sandpiper gives a swift descending flight with deep fluttering wingbeats and piping calls.
- The teetering motion unique to this species gave rise to their scientific name Actitis macularius, from the Greek aktites meaning “coast-inhabiting” and macularius meaning “marked”.
- Spotted Sandpipers will opportunistically forage nocturnally on moonlit nights, when prey may be more active.
- Rather than migrate in flocks, Spotted Sandpipers migrate individually at night and remain solitary even on their wintering grounds.
- Some Spotted Sandpiper populations are now wintering farther north than previously, possibly due to warmer winter temperatures.
Conclusion
From their distinctive teetering walk to their remarkable gender role reversal, Spotted Sandpipers stand out as a unique shorebird. Their vast breeding range, polyandrous mating, solitary nesting habits, and precocial young are all evolutionary adaptations that have allowed them to remain abundant despite threats facing other shorebird species. With their cryptic spotted plumage and incessant tail bobbing, the Spotted Sandpiper is one of our most recognizable and fascinating shorebirds.