Spotted sandpiper

Spotted sandpipers are a philopatric species.[3] Their breeding habitat is near fresh water across most of Canada and the United States. They migrate to the southern United States, the Caribbean, and South America, and are very rare vagrants to western Europe. These are not gregarious birds, and are seldom seen in flocks. Spotted sandpipers are the most widespread species of their kind in North America due to their high breeding rates and their ability to adapt to various environmental pressures.[3]

'Record shot' of Spotted Sandpipers at Île Sainte-Hélène in Montreal, Canada, showing diagnostic features such as the all-brown back & tail (i.e. no black, unlike many other sandpipers), white leading and trailing edge to the wings, partial white wingbar, and white edging to tail.

Adults have short yellowish legs and an orange bill with a dark tip. The body is brown on top and white underneath with black spots. These spots vary in degree over the course of spotted sandpipers' lives, becoming especially prevalent around the breeding season. The overall health of spotted sandpipers may be suggested by the "spottiness" of an individual. Generally, females with more "spottiness" were healthier than those who did not have as many spots. The condition of males based on the amount of spots they exhibit is yet to be determined. Additionally, spot size gets smaller and the spot shape becomes more irregularly shaped as age increases. Spotted sandpipers also feature a white supercilium.[4]

Non-breeding birds, depicted below, do not have the spotted underparts, and are very similar to the common sandpiper of Eurasia; the main difference is the more washed-out wing pattern visible in flight and the normally light yellow legs and feet of the spotted sandpiper. The Actitis species have a distinctive stiff-winged flight low over the water. They also have a distinctive walk in which their tails bob up and down. Males and females exhibit similar physical measurements, but differ in weight; females tend to be about 20-25% heavier than males.[3]

Measurements:[5]

• Length: 7.1-7.9 in (18–20 cm)
• Weight: 1.2-1.8 oz (34-50 g)
• Wingspan: 14.6-15.8 in (37–40 cm)

Breeding grounds are chosen based on various environmental factors, but tend to be in the proximity of bodies of water that offer some coverage from vegetation. Successful breeding sites may be used repeatedly until either the site becomes physically unsuitable (from overgrown vegetation or flooding) or predation becomes too severe. The females usually arrive at breeding grounds before the males do and establish their territories. Males arrive to breeding sites later, but it is uncertain whether or not they will arrive to the same breeding sites that some females have chosen.[6] The search for mates amongst female spotted sandpipers is much more competitive than finding potential mates is for males.[3]

During each summer breeding season, females may mate with and lay clutches for more than one male, leaving incubation to them. This is called polyandry. Male spotted sandpipers take care of the offspring, both before and after the offspring hatch. They will incubate their eggs for about 20–23 days.[3] Male parents of first clutches may father chicks in later male's clutches, probably due to sperm storage within female reproductive tracts, which is common in birds. Females that fail to find additional mates usually help incubate and rear chicks. "Prior to incubation, blood plasma concentrations of testosterone and dihydrotestosterone are substantially higher in males than in females" and these levels plummet 25-fold in males as incubation proceeds.[7] Additionally, mated females have testosterone concentrations that are 7 times higher than those of unmated females.[7] Due to their polyandrous behavior, spotted sandpipers tend to produce more offspring compared to other species of sandpipers.[6]

These birds forage on ground or water, picking up food by sight. They may also catch insects in flight. They eat insects, crustaceans and other invertebrates. As they forage, they can be recognized by their constant nodding and teetering.

The main predators of spotted sandpipers include raptors, mustelids, mice, and gulls. Most of these predators target the sandpipers' chicks and eggs.[8]

Although there has been some decline in the population of spotted sandpipers, their conservation status is currently of least concern. However, the decrease of spotted sandpipers is not projected to slow or stop in the future. The destruction of their natural habitats due to increasing wildfires causes problems for breeding and raising offspring. Additionally, the gradual increase in temperatures poses a problem for newborn sandpipers.[9]

Eggs, Collection Museum Wiesbaden

• 
  Front view
• 
  Non-breeding plumage
• 
  Spotted Sandpiper hunting in the Wallkill River Wildlife Refuge in New Jersey and New York (state)
• 
  Spotted Sandpiper foraging in Fox River Grove, Illinois

• Vinicombe, Keith (2006) ID in depth: Spotted Sandpiper Birdwatch 171: 29-31

Wikimedia Commons has media related to Spotted Sandpiper.

Wikispecies has information related to Actitis macularia.

• Spotted Sandpiper Species Account - Cornell Lab of Ornithology
• Spotted Sandpiper - Actitis macularia - USGS Patuxent Bird Identification InfoCenter
• "Actitis macularius". Integrated Taxonomic Information System.
• "Spotted Sandpiper media". Internet Bird Collection.
• Spotted Sandpiper photo gallery at VIREO (Drexel University)