The Benefits of Commitment in Black-headed Gulls

By: Karina Rodrigues, Joanna Soliman, Yenifer Oseguera, and Giana Youssef (Stonehill College, BIO323: Evolution, Spring 2023)

Overview

Loyalty, a quality some lack and some do not. Have you ever thought about the positive effects loyalty has on people, better yet species? In terms of evolution, loyalty translates to how committed a species is to its breeding partner. Originating from the Netherlands, black-headed gulls (Chroicocephalus ridibundus) were used to study the benefits of long-term relationships and if it plays a role in how parents invest more with their partners as well as their pair bond with one another. These seabirds were studied in a model environment that fits the birds natural needs in order to exhibit their natural behaviors. After testing different mechanisms, selection for mate retention reduces parental care conflicts between a pair and also sheds light to selecting traits that increase individuals fitness throughout evolution.

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Why do birds get divorced?

Divorce in Savannah Sparrows of Kent Island

by: Michael Calcagno, Meghan Ghazal, Lizzie Poyant & Zarir Sidhwa (Stonehill College Evolution Fall 2017)

In Savannah sparrows (Passerculus sandwichensis) that reside on Kent Island, New Brunswick, Canada an understanding of divorce rates within the species was analyzed to determine the molecular basis of the phenotypic trait. As well as, to determine if divorce is an adaptive strategy for greater fitness for females. In this species, approximately 47% of pairs in which both partners survived to the following breeding season ended in divorce. Neither the lifetime number of divorces nor whether an individual had ever divorced affected the fitness of either sex, thus suggesting little to no sexual selection for the trait. Divorce in the Savannah sparrows appeared to be an inheritable behavior in which expression depending primarily upon an individual’s age, mating status, sex, and size.

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