There are more than 11,000 species of birds in the world, but only four have populations of 1 billion or more, among them the ring-billed gull (Larus delawarensis). (The others: house sparrows, European starlings and barn swallows.) The numbers of gulls have increased massively in the past hundred years because of the increase in human food waste, and because gulls are protected under the U.S. Migratory Bird Act of 1918.
This is probably the gull you see stealing sandwiches on the beach or circling around french fries spilled in a McDonald’s parking lot. They are opportunistic feeders who will eat whatever is available and easiest to get: fish, mollusks, insects, eggs, crabs and human garbage. Scientists have analyzed their coughed-up pellets, which like owl pellets contain indigestible bits. They found, among other things, pork bones, plastic wrap, aluminum foil, paper towels and pieces of rubber, metal and glass. Canadian scientists analyzed the food adult gulls feed their young, learning that 70 percent was human garbage (meat, bread, fries), 9 percent worms, 8 percent insects and 7 percent small mammals. These scientists also concluded that the human food had the greatest energy content of all the foods.
Ring-billed gulls are small, about the size of a crow. They get their name from a black ring around the tip of their yellow bills. (Although a common sight, they do not breed in Massachusetts: Their spring breeding grounds are in Canada, Northern New England, Great Lakes region and Pacific Northwest.)
Although people call it a seagull, the ring-billed gull can be found inland far from the ocean. During the day, gulls rest and scavenge for food. At night, they roost in large groups on lakes or at sea where they feel safe from predators. In the 1990s, the Department of Conservation and Recreation realized that gulls roosting on the Wachusett and Quabbin reservoirs were causing fecal coliform bacteria numbers to skyrocket – gull feces contain greater amounts of fecal coliform bacteria than those of geese. So in 1993, officials implemented a bird harassment program to keep the birds from roosting on water used for human consumption. This program is in effect from late summer to April and has been effective in maintaining water quality.
Gull droppings are not just found in our reservoirs. Their whitish droppings can be found below areas in which they scavenge, roost or fly over. Bird urine is different from human urine. In humans, the kidneys filter waste products from the blood, which are then stored in the bladder as watery urine. In birds, 95 percent of that water is reabsorbed. The remaining waste becomes a white suspension containing uric acid crystals. Birds do not have a bladder, and do not store their waste. To fly, birds need to be as light as possible, so they drop their waste immediately rather than storing it in a bladder.
Land animals store urine to avoid leaving behind a scent trail. They release urine only when they find a safe area away from their home. Birds, however, do not need to worry: When they fly, predators cannot reach them, and when they roost on open water, they are far from predators. Therefore, birds do not hold onto their waste.
All birds have a cloaca (from the Latin for “sewer”). It is an all-purpose opening through which birds expel waste, lay eggs and pass sperm. Their white uric acid waste moves from the kidneys to the cloaca. Feces from the intestines also moves to the cloaca. The two mix into the white sludge we all know as bird droppings.
The white part of gull droppings is comparable to human urine. Within the white paste are green or brown masses (the stool), which are undigested remnants of food. So bird droppings are pee and poop in one blob. Uric acid does not dissolve in water easily, so gull poop can be difficult to get off your car or outdoor furniture. According to the WD-40 website, one of its 40 uses is to remove baked-on bird droppings quickly from car exteriors. (I’ve never tried this myself, so attempt removal at your own risk.)
Discussing gull cloacas leads to another interesting question: How do ring-billed gulls have sex? Male gulls, like most birds, do not have a penis. During breeding season, though, the cloacas of males and females swell and stick out of their bodies. The male climbs on top of the female, both facing the same direction, and the female spreads her tail feathers to expose her cloaca. The male rubs his cloaca against the female’s (known as a cloacal kiss), transferring sperm to the female. The cloacal kiss lasts for only about a second, so you may have seen this activity without even knowing what had transpired.
Ring-billed gulls have no trouble flying to new locations in search of food. They can travel from Maine to Florida in only a couple of days. Most ring-billed gulls in Massachusetts drift south in winter, ranging from Rhode Island to Florida. The ring-billed gulls you see in Massachusetts in winter are usually more northern birds that have drifted south to Massachusetts. Even these birds tend not to stay for the entire winter and continue drifting even farther south.
Eighty percent of the birds roosting at the Quabbin and Wachusetts reservoirs are ring-billed gulls. To learn more about them, biologists banded 880 ring-billed gulls from 2008 to 2011. Some were also fitted with radio transmitters. These tagged gulls were later spotted from Canada to Florida. One gull with a radio transmitter spent its days in parking lots in fall and winter. In spring it fed on worms in fields. It also traveled to wastewater treatment plants, landfills and parks. It roosted at night in both freshwater lakes and saltwater seas.
Many adults leave their northern breeding grounds at the end of June. Gulls like to forage in open areas where they can spot predators, so parking lots or roofs are superb locations in which to spot them.
Have you taken photos of our urban wild things? Send your images to Cambridge Day and we may use them as part of a future feature. Include the photographer’s name and the general location where the photo was taken.
Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.
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I treasure these articles and send them to all of my friends!
Thanks, Jake! I’ll make sure Jeanine sees this.
I also love Jeanine’s Wild Things articles and often send them out to others. Continuing thanks to her, and also to Richard George for his spectacular photos.