20. Parental Care

20. Parental Care

Altricial

(naked, blind, immobile, cannot self-feed, cannot regulate body temp)

Precocial

(downy, mobile, self-feeding, better temp. regulation)

Altricial species yolk content

• lay “cheap” eggs (20% yolk content) and have a short incubation period. Nestlings are still embryos when the egg hatches

Precocial species yolk content

• have “expensive” eggs with 40-50% yolk content. The extra energy is needed to fuel longer embryo development period. Higher cost of egg production and longer incubation period, but chicks are relatively mature upon hatching

Altricial vs. Precocial chick growth rate

• Small songbird chicks (altricial) weigh 10% of adult mass at hatching, but attain adult mass (and fledge) at only two weeks of age

• Although precocial chicks are relatively mature at hatching, they grow more slowly than altricial chicks because they feed themselves

altricial cavity and open-cup nesters

• cavity nesters slower than open-cup nesters, open-cup ground nesters the fastest

• more exposed to predators and harsh weather

Lesser Black-backed Gull clutch size experiment setup

• Removed 1 egg during egg laying to force female to lay a 4th egg in order to achieve a normal final clutch size (3 eggs)

• Compare to control females that only laid 3 eggs

Lesser Black-backed Gull clutch size results

• Females ‘induced’ into laying 4 eggs lost an extra 5% of body mass during egg-laying

• 4-egg females lost far more pectoral muscle (protein condition index) which was used as an energy source in egg production

Lesser Black-backed Gull carry over effects

• Experimental females reared 30% fewer chicks than control females and were 3 times as likely to fail at nesting

• Experimental females also produced smaller fledglings, which in turn are less likely to survive to adulthood

Common Eider costs of incubation

• (arctic ducks) females incubate eggs alone, and do not eat during the 25 day incubation period

• Females lose about 20% of their body mass during incubation

Common Eider experiment and results

• Manipulate clutch to produce 3-egg nests (low incubation demand) and 6-egg nests (high incubation demand)

• Measure body mass and lymphocyte levels

• Lower lymphocyte levels are indicative of immuno-suppression and increased susceptibility to infections

• Incubating 6-eggs was more costly

Common Eider experiment carry-over effects

• Carry-over costs to lay date and clutch size in the following year

• High incubation demand = later lay date and smaller clutch size

Black-legged Kittiwake experiment

• removed eggs from nests in late incubation (simulating predation) to reduce chick feeding effort to zero

• Compared adult survival and future reproductive success with un-manipulated nests (where parents did have young to feed)

• no young had higher survival rates

Black-legged kittiwake carry-over effects

• Parents who fed young during the experiment (un-manipulated) experienced lower fledging success the next year

• The high energetic cost of parental care has long-lasting effects on fitness

Carry over effect for Collard Flycatcher from costs of feeding young

• >parental effort = later fall migration departure & arrival at African overwintering sites, but, dissolves by spring

Cross-fostering chicks of different ages results

• extend/reduce parental effort duration by 25%

• Result: more effort = later fledge, migration, shorter winter, later breeding next year, lower RS etc.

Eurasian Jackdaw experimental setup

• Studied jackdaws in nest box populations in Netherlands from 2004-2012

• Brood size was experimentally increased, or decreased by 2 nestlings

• Some parents received the same treatment for several years

Results of Eurasian Jackdaw experiment

• For all individuals in the study (a) parents with enlarged broods had a 0.6 annual probability of survival compared with 0.72 for parents with reduced broods

• The difference was far greater for those parents who were given enlarged broods in > 2 years

Senescence

a decreased annual probability of survival with increasing age

Rearing efforts effect on senescence

• increases rate of senescence

• Parents with enlarged broods (blue, dashed line) had a faster rate of senescence than parents with decreased parental effort (red, solid line)