Reduced chick performance makes supernormal clutches maladaptive in a shorebird

Area of Science:

• Evolutionary biology
• Ornithology
• Life-history theory

Background:

• Life-history theory predicts offspring number/quality trade-offs, but clutch size is often fixed in birds.
• Shorebirds (Charadriiformes) typically lay four eggs, with evolutionary constraints on clutch size debated.
• Parental incubation capacity is a hypothesized constraint on shorebird clutch size.

Purpose of the Study:

• To experimentally test if parental incubation capacity constrains clutch size in Common Ringed Plovers (Charadrius hiaticula).
• To investigate potential post-hatching effects of enlarged clutches on chick development and survival.

Main Methods:

• Experimental clutch enlargement in Common Ringed Plovers.
• Comparison of hatching success, chick size, mortality rates, embryonic growth (mass loss), incubation period, and hatching synchrony between control and enlarged clutches.

Main Results:

• Chicks from enlarged clutches were smaller and had higher mortality rates during the first two weeks.
• Enlarged clutches showed slower embryonic growth, longer incubation periods, and more asynchronous hatching.
• Hatching success was largely unaffected, but negative post-hatching effects were evident.

Conclusions:

• Parental incubation capacity, and subsequent post-hatching resource allocation, likely constrains clutch size evolution in shorebirds.
• Laying additional eggs may be disadvantageous due to negative impacts on offspring quality and survival.
• Post-hatching constraints are crucial for understanding clutch size evolution in shorebirds.