The Birds of Kent Island
written by Hayley Ann Spina
photography by Hayley Ann Spina
Kent Island, New Brunswick
Kent Island, NB is an 80-ha island located 9 km south of Grand Manan Island in the Bay of Fundy. The Island is home to numerous avian species, and temporarily home to the many researchers that visit the Bowdoin Scientific Station each summer. For my PhD research, I have the pleasure of visiting Kent Island during the breeding season (end of May to early August), to study the breeding ecology of the Savannah Sparrows. The long-term study of Kent Island's Savannah sparrows was started in 1987 by Dr. Nathaniel T. Wheelwright. Current research on Savannah sparrows is conducted by the Norris lab and the Newman lab at the University of Guelph, the Mennill lab and the Doucet lab at the University of Windsor, and by Heather Williams at Williams College.
The Savannah Sparrows
A Savannah Sparrow. While Savannah sparrows look similar to other sparrows, they are most easily identified by their yellow eyebrow stripe
Savannah sparrows are migratory, grassland songbirds that are abundant across North America. They are an excellent study species, as they are highly philopatric, meaning that even though they migrate to the Southern USA over the winter, surviving sparrows will return to the island to breed; so sparrows that are born on the island can be monitored over their entire lives. Sparrows have such high site fidelity that first year breeders lay their first nests a median distance of 228m from the nest they were born into (Wheelwright and Mauck, 1998). At the beginning of the season, males will establish territories, which are ~40m2 areas that they will defend from other Savannah sparrows. A male will attract a female partner by singing from perches throughout his territory, and his partner will make her nests within his territory. Nests are laid within grasses or bushes in open fields, so they are easily accessible to the researchers.
Savannah sparrows have been studied almost every year on Kent Island since 1987. Every year, all sparrows within two open fields on the island (1-ha and 6-ha) are identified, and the territory boundaries of all mating pairs are determined. Any birds that are not already banded are captured briefly, given a metal ID band, and 3 colour bands, for easy visual identification during the breeding season.
South Field, Kent Island. The Bowdoin Field Station - where the researchers cook, sleep, and conduct lab work - can be seen in the background
A banded Savannah sparrow. Birds are named by their colour bands, with each colour having a representative letter associated with it. Colours are read left to right. This bird is RO.Y.
To catch a sparrow, we set up large, fine-mesh nets called mist nets, and wait for sparrows to fly into the nets. There are several techniques used to catch a sparrow. Passive mist netting involves setting up a long row of nets and hoping that unsuspecting sparrows will fly into the nets. This technique works well in high-density areas, when we are not interested in targeting a specific individual. When we need to band a specific male or female bird, we use two different targeted mist netting strategies. To catch a male of interest, we will set up nets on his territory, and set up a speaker underneath the net that plays a Savannah sparrow song. The male will think that the speaker is another male that has snuck onto his territory and is trying to mate with his female. He will attempt to chase off this “bird” and end up caught in the mist net. To catch a female, we set up nets surrounding her nest, and wait for her to return to incubate or feed her nest. Once she is at her nest, we approach her nest to flush her into the net.
A researcher setting up mist nets.
Passive mist netting. The researchers wait patiently for sparrows to fly into their row of nets.
Once the bird is banded, we take morphological and physiological measurements. We measure each sparrows wing length, tarsus (leg bone) length, bill length, bill depth, and mass. We also collect a small blood sample to collect the bird’s DNA. Female sparrows will often cuckold their partners and sneak off to mate with other males. Therefore, the only way to determine a nestling’s paternity is by DNA analysis. Over 50% of nests in a breeding season may contain offspring from multiple fathers (Freeman-Gallant, 1997)!
A savannah sparrow in hand.
Banding a Savannah sparrow.
Measuring Savannah sparrow bill length.
In addition to banding, we locate all of the Savannah sparrows’ nests within the Island’s two open fields. Nest searching can be time-consuming work, beginning in the early hours of the morning, when birds are most active. To find a nest, researchers typically spend hours watching a female sparrow, patiently waiting for her to return to her nest. From sunrise to sundown, the females spend the day alternate between incubating their eggs and foraging for food. The female performs all nest building and incubation without the help of her partner, so we only watch the female when nest searching. The researchers must stay hidden from the birds, because if the birds know they’re being watched then they may alter their behaviour. We watch for specific behaviours that are clues that a female is approaching her nest. Once we spot a female going down to the same spot multiple times, we will have a rough idea of where her nest is. We approach the nest as quietly as possible, until we are within a few metres. Then, using a long stick, we begin brushing the grasses in front of us until we see the female flush up. We keep our eyes on the spot where the female emerged and search carefully but thoroughly until we find the nest. Some nests are relatively easy to find, and others are so well hidden, they take days to locate, even when we have a good idea of where the female is flushing up from. Most often nests are found at the egg stage, but sometimes females will be so sneaky, nests are not found until they have hatched. While challenging, nest searching is very rewarding, and (friendly) nest searching competitions are often enjoyed by the researchers.
A Savannah sparrow nest with eggs.
Once the researchers find a nest, the nest is then protected from predators. Predation rates by avian predators (primarily North American Crows) is high on Kent Island. Placing exclosures over the nests prevents the crows from access to the Savannah sparrow nests, but parents are still able to access the nest through the gaps. Exclosures are very successful at preventing predation. Almost every nest that is protected survived to the fledgling stage (when the birds leave their natal nest).
A predator exclosure protecting a Savannah sparrow nest.
An exclosure overtop of a Savannah sparrow nest in the blueberry brush.
Once nests are protected, the researchers monitor them to determine the day that the nestlings hatch. Once nestlings are 7 days old, we band them with a numbered ID band and 1 colour band, take morphological measurements, and collect samples such as small blood samples, fecal samples, and feather samples for physiological measurements once we return to the lab.
A banded 7-day-old Savannah sparrow. Nestlings open their mouths wide in hope that mom or dad will bring something to feed them.
A handful of nestlings. Savannah sparrows will typically have 3-5 nestlings within one nest. By day 7, nestlings weigh up to ~15 grams.
Once nestlings are 9-11 days old, they begin to fledge, meaning they leave their nests on their journey to independence. Fledglings begin to fly shortly after fledging and continue to be fed by their parents for another 1-2 weeks.
A female Savannah sparrow ready to feed her offspring.
Once fledglings are able to feed independently, parents will end care for their offspring, and the juvenile birds will remain on the island until early September, when they begin to depart for migration. Parents that have successfully fledged a nest early in the season may attempt to have a second nest within the breeding season, known as double brooding. For the researchers, this means a second round of nest searching, monitoring and banding. However only an average of 29% of females in the population will double brood (Woodworth et al., 2017), leaving the researchers some time to explore the island and the other birds that live there in the second half of the summer.
Other Aves of Kent Island
Savannah sparrows are not the only birds that inhabit Kent Island! Below are three other species I had the pleasure of experiencing and learning about.
American Herring Gulls
Arguably, the cutest birds on the island are the thousands of baby herring gulls that are born around the same time as the Savannah sparrow nestlings. But don’t let these adorable faces fool you. These babies grow up to present some of the biggest challenges for the Kent Island researchers. The gulls commit infanticide on neighbouring babies, meaning they attempt to kill the babies of other gulls. Unfortunately for the researchers, gulls haven’t learned to distinguish the difference between a gull and a human and coming too close to a gull nest will likely result in a gull flying full force toward your head. Researchers on Kent Island have been known to wear hard hats to avoid these skull cracking experiences. See this post to hear what thousands of screaming gulls sound like, and to see how nest searching sticks dually serve as gull protection!
Juvenile American herring gulls
Herring gulls circling an unexpecting researcher. There is a gull baby within these grasses, somewhere!
The chaos of the Herring Gull breeding season. This photo accurately depicts the commotion that constantly surrounds the baby gulls in their first few months of life.
Leach's Storm Petrels
One of the most impressive species of birds that nest on Kent Island are the Leach’s storm petrels. These fascinating little seabirds have been studied on Kent Island since 1954. Petrels can live to be 40 years old and migrate to the Western coast of Africa over the winter. Though there are more than ~20,000 breeding pairs on the island (d’Entremont et al., 2020), visitors to Kent need to get lucky to spot these secretive seabirds. Petrels make their nests in burrows underground, and only emerge late at night when they fly out to sea to forage. Though, if you’re awake in the earliest hours of the morning, you may likely to hear their terrifying calls (they sound like evil clowns. Seriously. Check it out). We were very excited to have Dr. Laura Tranquilla from Bird’s Canada visit and teach us about the petrels! To access the petrels, the researchers will partake in an activity called “grubbing”, which involves reaching your arm deep into a petrel burrow, and carefully extracting the bird.
The openings to a petrel burrow.
“Grubbing” for a storm petrel. Long, skinny arms are ideal for petrel grubbing!
A Storm Petrel egg. Storm petrels will lay one egg per year.
(“Grubbing” for a storm petrel. Long, skinny arms are ideal for petrel grubbing!
An adult storm petrel.
The large wingspan of a Leach’s storm petrel.
Black Guillemots
Black guillemots are seabird that have been documented breeding on Kent Island since the 1940’s (Winn, 1950)! Guillemots nest on the small rocky cliffs of Kent Island and forage close to shore for fish or invertebrates. While guillemot research was not occurring during my time on the island, we enjoyed an afternoon of watching these birds bask in the sunshine and forage on the Bay.
