Delayed post-juvenile moult in malaria-infected Eurasian blackcaps

Area of Science:

• Ornithology
• Parasitology
• Ecology

Background:

• Parasites significantly impact host fitness by depleting resources crucial for life-history stages.
• Post-juvenile moult (PJM) is a critical feather replacement phase in young birds, affecting their preparedness for future challenges.
• The influence of parasites on PJM remains understudied in avian species.

Purpose of the Study:

• To investigate the relationship between haemosporidian infections and the progress of post-juvenile moult in juvenile Eurasian blackcaps (Sylvia atricapilla).
• To determine if parasite presence and abundance affect the timing and completion of PJM.

Main Methods:

• Analysis of blood samples from 435 juvenile Eurasian blackcaps across 26 localities in Iberian Spain over three years.
• Assessment of haemosporidian parasite genera (Haemoproteus, Plasmodium, Leucocytozoon) presence and abundance.
• Statistical control for body condition, sex, year, and capture date to evaluate moult scores.

Main Results:

• Infected blackcaps exhibited delayed post-juvenile moult, indicated by lower moult scores.
• Plasmodium infections and high intensities of Haemoproteus parasites were particularly associated with delayed moult.
• Co-infections also contributed to delayed PJM progression.

Conclusions:

• Haemosporidian parasites impose fitness costs on birds by delaying critical life-history events like post-juvenile moult.
• Delayed plumage acquisition can negatively affect a bird's ability to cope with subsequent challenges, such as winter survival and migration.
• This study highlights the broader fitness consequences of haemosporidian infections in avian populations.