Mapping the premigration distribution of eastern Monarch butterflies using community science data

Using community science to map western monarch butterflies (Danaus plexippus) in spring

Migratory animals follow seasonal cycles comprising linked phases often with different habitat requirements and demographic processes. Conservation of migratory species therefore must consider the full seasonal cycle to identify points limiting population viability. For western monarch butterflies, which have experienced significant declines, early spring is considered a critical period in the annual population cycle. However, records of western monarchs in early spring, when overall abundance is lowest, have historically been extremely limited. We used a community science initiative, the Western Monarch Mystery Challenge, to collect data on monarch distribution throughout the western United States between February 14th and April 22nd over 3 years. Using data from the Western Monarch Mystery Challenge and iNaturalist, we identified potential breeding habitat for western monarchs in early spring that spanned a large geographic area and several ecoregions. We observed monarchs in early spring that likely eclosed in the current year, suggesting that population expansion from overwintering sites reflects both movement and population growth. The number of records of western monarchs from early spring was higher during the Mystery Challenge (33.0/year) than earlier years (5.1/year). This study demonstrates the potential for and limitations of community science to increase our understanding of species at points in the life cycle when they are rare.

Nutritional state variations in a tropical seabird throughout its breeding season

Individual body condition is frequently used to explain differences in foraging and breeding ecology in seabirds. However, little is known about the covariations of body mass with the nutritional state of animals as measured through plasma metabolites and how these different measures vary between and within individuals during breeding. Here, we assessed intra-individual variations of plasma metabolites (triglycerides, cholesterol, protein, and ß-hydroxybutyrate concentrations) and in body mass of Blue-footed boobies (Sula nebouxii) throughout their breeding season 2011-2012 in Isla El Rancho, Mexico. We found breeding-stage and sex-specific variations in individuals' plasma metabolite concentrations, but these did not mirror variations in body mass. Before egg-laying, females had higher triglycerides, cholesterol, and protein concentrations than males. In contrast, males used their nutritional reserves (higher ß-hydroxybutyrate concentrations) more than females during the breeding season (except for early chick-rearing). At the individual level, males gained weight during the breeding season, whereas females lost weight. We also found that between-individual differences in plasma metabolite concentrations and changes in body mass were not consistent throughout the breeding season, while individual body mass was significantly repeatable. This study contributes to a better understanding of seabird breeding ecology and physiology by showing that sex-specific breeding roles might highly influence the nutritional state. Similar patterns might occur in other seabird species, helping to explain why we can find stage- and sex-specific foraging behaviors even in monomorphic species.