The importance of having a partner: male help releases females from time limitation during incubation in birds

Table 2 Structure of fitted models and their associated hypotheses or questions

Model	Response variable	Predictors	Species	Hypothesis or question
1	Total nest attentiveness	Male attentiveness, body mass, hemisphere, latitude	Shared incubation	Total nest attentiveness increases with the intensity of direct male help
2	Total nest attentiveness	Female attentiveness, body mass, hemisphere, latitude	Shared incubation	Total nest attentiveness and female contribution to attentiveness are not correlated
3	Female attentiveness	Male attentiveness	Shared incubation	Male contribution increases with total nest attentiveness, female contribution does not
4	Total nest attentiveness	Incubation feeding, body mass, hemisphere, latitude	Incubation feeding	Total nest attentiveness increases with the intensity of indirect male help
5	Total nest attentiveness	Incubation category, body mass, hemisphere, latitude	All	Male help (direct or indirect) increases average total nest attentiveness. Do direct vs. indirect male help differ in their effects on average total nest attentiveness?
6	Female nest attentiveness	Incubation category, body mass, hemisphere, latitude	All	Does direct male participation change average female incubation effort?

In models 1 and 2, we fitted an interaction of male or female attentiveness with hemisphere; in model 4, an interaction of incubation feeding with hemisphere. In models 5 and 6, we fitted two-way interactions of incubation category with hemisphere, latitude, and body mass.
Predictors include incubation category (female-only care, incubation feeding, shared incubation), male care (present vs. absent), body mass (g), hemisphere (North vs. South), and absolute latitude (between 0 and 90).

ISSN: 1742-9994