Avian Brood Parasitism: Variation
in Host Response
What is Brood Parasitism?
• Obligate vs. Facultative
Host vs. Parasite
•Parasites benefit, at the cost of the host
•Co-evolutionary arms race often occurs
between the host and the parasite
Frontline Defenses
• Mobbing-alarm calls, physical attacks • 2 purposes
- prevent parasitic egg laying
Egg Rejection
• Discrimination among eggs • Two forms
- ejecting parasitic egg from nest
-abandoning entire nest
• How do hosts know when to reject?
- visual cues (spotting, size, brightness,etc.) - egg arrangement
Spottiswoode, C.N., and Stevens, M. (2011). How to evade a coevolving brood parasite: egg discrimination versus egg variability as host defences. Proc Biol Sci 278, 3566–3573.
Polačiková, L., Takasu, F., Stokke, B.G., Moksnes, A., Røskaft, E., Cassey, P., Hauber, M.E., and Grim, T. (2013). Egg arrangement in avian clutches covaries with the rejection of foreign eggs. Anim Cogn 16, 819–828.
Chick Rejection
• Less common than egg rejection • 2 forms:
- Physically remove chick - Abandon entire nest
• How do host know when to reject?
-amount of parental care required -incubation call as password
Influences on Host Response
• Variety of defenses seen in hosts • Influenced by:
-parasitic pressure -parasitic species
-host personality/behavior • Host that do not defend:
-evolutionary lag
To Conclude…
• Brood parasitism benefits the parasite, at the cost of the host
• Host use variety of defenses to avoid parasitism
• Which defense is used, and when, is dependent upon the specific situation • Some hosts choose to accept parasitism
