Feather hole
Feather holes are feeding traces of lice, likely Brueelia spp.
Feather holes are characteristic damages found on the wing and tail feathers of some small-bodied passerines, particularly barn swallows. They have been widely used as a proxy for quantifying the intensity of infestation by avian lice, specifically Machaerilaemus malleus and/or Myrsidea rustica, though recent evidence has challenged this assumption.
- Type
- Feather damage
- Associated parasites
- Machaerilaemus malleus, Myrsidea rustica, Brueelia spp.
- Host species
- Small-bodied passerines, especially barn swallows
- First use as proxy
- Based on assumption of chewing by Machaerilaemus malleus
- Current best fit
- Brueelia spp. lice (Ischnocera)
Lore & Background
Feather holes were initially observed on wing and tail feathers of small passerines, with barn swallows being a key study species. Researchers suggested the holes were feeding traces of the avian lice Machaerilaemus malleus and/or Myrsidea rustica. Hole counts proved highly repeatable, leading to their use as a measure of infestation intensity.
Reader's Guide
Feather holes became a cornerstone for studying host-parasite interactions, with numerous influential papers linking hole counts to sexual selection, feather breakage, flight performance, immunity, arrival dates, and song characteristics. Cross-fostering experiments indicated that infestation levels were heritable. However, a recent finding that Machaerilaemus malleus is absent from Europe—where all such studies occurred—undermined the original assumption. Correlational evidence now suggests that Brueelia spp. lice provide the best fit for the distribution and abundance of feather holes in barn swallows and other small passerines, leaving the exact causal agent in dispute.
Did You Know?
- Feather holes were originally attributed to Machaerilaemus malleus and/or Myrsidea rustica.
- Hole counts were shown to be highly repeatable and used as a measure of infestation intensity.
- Cross-fostering experiments demonstrated that infestation levels were heritable.
- Machaerilaemus malleus has been recorded in Europe, and feather hole studies have been conducted in both Europe and North America.
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