Large gull species, such as Herring Gulls and Western Gulls, exhibit social monogamy, often maintaining a pair bond that lasts for many breeding seasons, sometimes spanning the bird’s entire reproductive life. This partnership is maintained year-round or quickly re-established when the gulls return to their colony each spring. The success of their reproduction hinges on this long-term bond, which facilitates coordination and shared parental duties. The death of one gull in a mated pair creates a significant disruption, impacting the surviving bird’s immediate behavior and future breeding prospects.
Immediate Behavioral Response to Mate Loss
Following the loss of a long-term mate, the surviving gull often demonstrates a notable alteration in behavior, frequently interpreted as distress. Individuals may spend time searching in the territory where the mate was last seen, sometimes exhibiting prolonged and unusual vocalizations. These long calls are distinct from typical aggressive or alarm calls and may represent an attempt to elicit a response from the missing partner. The intensity and duration of these reactions vary, depending on the strength of the pair bond.
The loss of a partner often leads to reduced focus on regular activities like feeding, as the bird’s attention is diverted to searching or increased vigilance. The surviving gull may also display heightened anxiety, especially if the mate was lost suddenly, such as through predation or human interference. This behavioral disruption is usually temporary, as the biological drive to survive and potentially breed again eventually takes precedence.
Reproductive Consequences for the Surviving Gull
The timing of the mate’s death determines the severity of the reproductive consequences for the surviving gull. If the loss occurs during the incubation or chick-rearing phases, the current breeding attempt is doomed to fail. Gull chicks and eggs require biparental care for successful development and survival, known as obligate biparental care. A single parent is unable to simultaneously guard the nest from predators, incubate the eggs, and forage enough to feed itself and the young.
Experimental removals confirm that one parent cannot sustain the effort alone; all deserted individuals abandoned the clutch or brood. The remaining parent, particularly a female, may continue to incubate and defend the nest for a period, but the eggs will eventually be lost to predation or neglect. Males have been observed to abandon the eggs significantly earlier than females after a loss. This failure means the surviving gull loses the entire reproductive effort for that season, a significant biological cost for long-lived species that invest heavily in each breeding attempt.
Strategies for Re-Pairing and Future Breeding Success
The long-term outlook for the surviving gull centers on its ability to re-enter the breeding pool, a process often influenced by the bird’s existing status. Gulls with high-quality territories or those that are older and more experienced tend to find new mates more quickly than younger, less established individuals. If the loss occurred late in the breeding cycle, the survivor waits until the following breeding season to seek a new partner.
Finding a new mate before the subsequent breeding season can help the widowed bird overcome disadvantages, such as a delayed start to egg-laying. Even with a new partner, the subsequent breeding success may be lower compared to long-term pairs, a phenomenon sometimes termed the “syndrome of the first-year bond.” This initial decrease in success is likely due to the time and energy needed to form a new bond and a lack of coordination. Despite the setback, the drive to reproduce ensures the surviving gull will eventually form a new pair bond and resume its reproductive life.