Piping plovers are small, sparrow-sized shorebirds that breed in North America. They get their name from their melodic, plaintive call which sounds like a high-pitched pipe being played. Piping plovers are light-weight birds, weighing only 1.5-2.5 ounces (42-70 grams) on average. Their small size allows them to nimbly run along sandy beaches, where they feed on invertebrates like marine worms, fly larvae, beetles, and crustaceans.
Typical Weight Range
The typical weight range for piping plovers is:
- Adult Males: 1.5-2.2 ounces (42-63 grams)
- Adult Females: 1.6-2.5 ounces (46-70 grams)
- Juveniles: 0.6-1.1 ounces (18-32 grams) at hatching
Adult females tend to be slightly heavier than males on average. The juveniles or chicks weigh less than 1 ounce when they first hatch from the egg. They quickly gain weight and are able to fly within about 25-35 days after hatching.
Factors Affecting Weight
Several factors contribute to variability in piping plover weights:
- Age: Chicks weigh less than 1 ounce at hatching. Their weight steadily increases until they reach adult size at around 1 year old.
- Sex: Females are usually about 5-15% heavier than males, possibly due to egg production.
- Time of Year: Plovers weigh less during migration and more during pre-breeding when they are storing extra energy for reproduction.
- Habitat Quality: Birds in higher quality habitats with more food availability tend to weigh more.
- Weather: Colder, harsher weather can cause temporary weight declines if food is scarce.
- Health: Parasites, diseases, and injuries can negatively impact body weight.
The interplay of these factors results in the range of weights observed in wild piping plovers throughout the year.
Measuring Weight in the Field
When studying piping plovers in the wild, scientists and bird banders carefully capture and measure birds to collect data on weight and other metrics. Some techniques for measuring plover weights include:
- Using a small portable electronic scale designed for weighing birds.
- Carrying a bag of shot pellets calibrated to known weights. This allows weighing by comparison.
- Using calibrated pendulum scales designed for small birds.
- Weighing nestlings by using a small portable scale or placing them in a bag with a known calibrated weight.
Researchers try to be quick and careful when handling plovers to minimize stress. However, collecting weight data along with banding allows tracking individual birds over time.
Changes in Weight Over the Year
Piping plovers go through seasonal weight fluctuations throughout the year:
- Winter: Plovers spend the winter along the Gulf of Mexico, Atlantic coast, and in the Bahamas. Food is plentiful and weights are normal.
- Early Spring: Birds start migrating north to breeding grounds in March and April. Weights decline during migration due to high energy expenditure.
- Breeding Season: From April to July, plovers aggressively defend breeding territories. Weights increase in preparation for breeding.
- Post-Breeding: Adults complete their breeding activities by late July and start migrating south in July and August. Weights decline during migration.
- Fall Migration: Plovers fly south from August through October. Weights remain low during migration.
- Return to Wintering Grounds: The birds reach their wintering grounds again in October and November. Weights stabilize with abundant food.
This seasonal cycle of weight gain and loss repeats each year for piping plovers. The small shorebirds nearly double their body weight before breeding season to sustain the high energy demands of reproduction.
Differences Between Male and Female Weights
Female piping plovers are slightly heavier on average than males. This weight difference is most pronounced right before breeding season when the females are developing and laying eggs.
For example, data from piping plovers in Ontario showed that just before breeding season:
- Females averaged 2.2 ounces (61 grams)
- Males averaged 2.0 ounces (57 grams)
This 10% weight difference between the sexes may be attributed to:
- Egg production – Female organs like the ovary and oviduct add weight.
- Fat stores – Females may pack on more fat to support egg laying and incubation.
- Larger body size – Females have slightly larger structural body size which adds weight.
However, the weight difference between the sexes varies over the course of the year and is smaller at certain times. For example, during fall migration, males and females are typically closer in weight after breeding responsibilities are over.
Weight Gain in Juveniles
Piping plover chicks weigh approximately 0.5-0.7 ounces (15-20 grams) when they hatch from the egg. Their weight steadily increases over the next 25-35 days as adults feed the chicks and they grow flight feathers.
The chicks follow a typical logistic growth curve, with the fastest weight gain occurring in the first two weeks after hatching. Their weight plateaus around the one month mark when they are close to adult size and ready to fly.
For example, one study of piping plover chicks in Ontario found:
- Hatching weight: 0.6 ounces (17 grams)
- 2 weeks: 0.9 ounces (25 grams)
- 3 weeks: 1.4 ounces (40 grams)
- Fledging at 4 weeks: 1.8 ounces (52 grams)
This rapid weight gain fuels the chicks’ growth and development. Adults must provision enough food as the chicks’ demand peaks in the few weeks after hatching. Reaching a fledging weight is crucial for survival.
Low Weight and Causes
While piping plovers maintain stable weights most of the year, low weights can occasionally occur due to:
- Migration: Long migration flights burn fat reserves, causing weight loss en route to breeding or wintering grounds.
- Parasites: Birds with intestinal parasite infections may fail to absorb nutrients efficiently.
- Sickness: Diseases like avian influenza depress appetite and raise metabolism.
- Starvation: On rare occasions, severe storms or food crashes can lead to malnutrition.
- Oil exposure: Foraging on oiled beaches after spills causes weight loss.
- Injury/stress: Birds recovering from injuries like predator attacks or human disturbance may lose weight.
However, piping plovers are resilient birds adapted to bounce back from harsh conditions. With adequate food and time to recover, their weights generally rebound back to normal levels. Only extended periods of starvation or chronic health issues lead to critically low weights.
Weight and Survival
Heavier piping plovers within normal weight ranges have increased chances of survival. Birds with more fat reserves are better equipped to endure periods of harsh weather, long migrations, or fluctuations in food availability.
For example, studies of piping plovers in the heavily oiled areas of the Gulf of Mexico after the Deepwater Horizon oil spill found:
- Surviving birds had up to 30% higher average body weights.
- Birds with lowest weights showed poorest annual survival.
This indicates birds in better condition were most resilient after this disruptive event. Maintaining adequate fat reserves helps piping plovers survive unpredictable threats. However, being slightly leaner may benefit migration as excess weight increases flight costs. A balancing act is required.
Weight Gain for Reproduction
Piping plovers gain significant weight before breeding season in order to reproduce successfully. Males and females with the highest pre-breeding weights are more likely to secure high-quality nesting territories, find mates earlier, and produce larger clutches of eggs.
For example, one study in Canada found:
- Heavier plovers arrived at breeding grounds 3-4 weeks sooner.
- Each 10% gain in pre-breeding weight predicted 10% larger clutch sizes.
- Heavier plovers produced up to 1.5 more eggs per clutch.
This pre-breeding weight gain gives plovers extra energy reserves to invest in vigorous courtship, egg production, and parental care once breeding begins. It directly translates into increased fitness and reproductive success.
Weight Loss During Breeding
While piping plovers gain weight before breeding starts, they often lose weight over the course of the breeding season while incubating eggs and provisioning chicks.
One study in the Great Plains tracked plovers and found:
- Pre-breeding weights averaged 2.1 ounces (60 grams)
- Mid-incubation weights declined to 1.9 ounces (54 grams)
- By chick-rearing, weights dropped further to 1.6 ounces (46 grams)
This seasonal weight loss is likely caused by the high energy demands of breeding. Incubation and foraging for chicks require extra expenditure of fat and muscle.
However, plovers can regain this lost weight quickly by feeding heavily after breeding duties end. Within a few weeks, most recover back to normal pre-migration weights.
Weight Compared to Other Shorebirds
Weighing only 1.5-2.5 ounces on average, piping plovers are among the smallest shorebirds in their coastal habitat. For example:
| Species | Average Weight |
|---|---|
| Piping Plover | 1.5-2.5 oz |
| Dunlin | 2.1-3.5 oz |
| Sanderling | 1.9-3.1 oz |
| Semipalmated Plover | 2.0-2.4 oz |
Their small size is likely an adaptation to foraging on narrow beach habitats and making rapid escape flights from predators. The tradeoff of a small body is that piping plovers cannot store as much fat internally compared to larger shorebirds. This makes maintaining adequate weight reserves critical for their survival and breeding.
Weights of Juveniles vs. Adults
Piping plover chicks weigh much less than adults and undergo rapid weight gain after hatching to reach adult size:
| Age | Avg. Weight |
|---|---|
| Chicks at hatching | 0.5-0.7 oz |
| Juveniles at fledging (3-4 weeks) | 1.5-1.9 oz |
| Adults non-breeding | 1.7-2.2 oz |
| Adults pre-breeding | 2.0-2.5 oz |
The chicks start at only 25-35% of adult weight but they nearly triple in size within a month. This fast growth requires huge amounts of food from the parents. After fledging, juveniles slowly gain additional weight and fat reserves until reaching adult weights by their first spring migration north.
Male vs. Female Weight Differences
Female piping plovers average 5-15% heavier than males, depending on the time of year:
| Sex | Non-Breeding Weight | Pre-Breeding Weight |
|---|---|---|
| Female | 1.8-2.2 oz | 2.1-2.5 oz |
| Male | 1.7-2.0 oz | 2.0-2.2 oz |
The weight difference is greatest leading up to breeding season when females gain extra fat to produce eggs. Male and female weights are more similar during non-breeding times once egg laying ends. However, the slightly larger body size of females accounts for persistently higher weight throughout the year.
Conclusion
In conclusion, piping plovers are diminutive shorebirds weighing only 1.5-2.5 ounces on average. Their small size helps them nimbly run along beaches but also limits fat storage. Plovers gain significant weight before breeding season to invest in reproduction. Females average 5-15% heavier than males depending on the time of year. Chicks hatch at just 0.5-0.7 ounces but quickly grow to near adult weight for fledging in 3-4 weeks. Maintaining adequate fat reserves helps piping plovers endure harsh conditions and unpredictable events during migration and breeding. Their light weight is a key adaptation to their extreme seasonal environments.
