Open AccessFactors associated with the mass of eggs laid by tree swallows Tachycineta bicolor varied yearly between 2008 and 2016 in Michigan
Author(s) -
Lombardo Michael P.,
Thorpe Patrick A.,
Otieno Sango,
Weglarz Dan,
Hawker Alyssa
Publication year - 2021
Publication title -
journal of avian biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.022
H-Index - 76
eISSN - 1600-048X
pISSN - 0908-8857
DOI - 10.1111/jav.02460
Subject(s) - biology , offspring , avian clutch size , nest (protein structural motif) , zoology , heritability , parental investment , ecology , demography , reproduction , pregnancy , evolutionary biology , biochemistry , genetics , sociology
The initial investment a female bird makes in an offspring is her production of its egg. The size of this investment can have important evolutionary consequences for both the female and her offspring. Between 2008 and 2016, we weighed 1977 tree swallow eggs freshly laid in nest boxes in west Michigan to investigate factors associated with egg mass. Breeding female age class was not associated with egg mass. Overall, eggs that hatched weighed significantly more than those that did not. An egg's mass was not associated with clutch size but increased with its position in the laying sequence. Females that bred multiple times showed high repeatability of egg mass. Mother–daughter narrow sense heritability of egg mass was low. There were statistically significant associations, both positive and negative, between female morphological characteristics and egg mass in some years but not others. Similarly, relationships between egg mass and weather conditions during egg formation were statistically significant in some years but not others. In summary, female characteristics and weather conditions were associated with tree swallow egg mass, but their influences varied yearly. These results reinforce the importance of long‐term studies for identifying the causes of selection that shape life‐history characteristics.