Nonsocial cues

Individuals may directly evaluate potential resources and constraints affecting success in a given activity (e.g., food availability, parasitism load, predator presence - Figure 6). If success is mainly linked to one factor, then this strategy should prove efficient to assess habitat quality. However, when this factor is difficult to assess, when many factors affect success, or when information on some factors is not available at the time of information gathering, an alternative is to use indirect cues revealing the effect of important factors, for example, chemical compounds revealing the presence of predators. Individuals can use search images of suitable habitats acquired during development (imprinting) or later (learning).

0.2 0.4 0.6 0.8 Temporal autocorrelation of patch quality (r)

0.2 0.4 0.6 0.8 Temporal autocorrelation of patch quality (r)

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O Philopatry

a Quality

X" ♦ Presence

T\ ■ Success

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i i

i i i

0.2 0.4 0.6 0.8 Autocorrelation coefficient

0.2 0.4 0.6 0.8 Autocorrelation coefficient

Figure 8 The value of 'public information', that is, the local reproductive success of conspecifics, for breeding habitat selection depending on environmental temporal predictability. In most seasonally breeding species, this cue will be available at the end of the breeding season, and can therefore only be used in the next year. It will thus be valuable only if the environment is autocorrelated from one year to the next. (a) In an optimality model, individuals choosing their breeding patch according to local reproductive success in the previous year (closed dots) achieve a higher lifetime reproductive success compared to individuals settling at random on a patch (open dots) only when the level of temporal autocorrelation of the environment is high. (b) Similarly, in a game theory model, strategies based on local reproductive success ('quality' and 'success') are selected for only when the level of temporal autocorrelation of the environment is sufficiently high. (a) From Boulinier T and Danchin E (1997) The use of conspecific reproductive success for breeding patch selection in territorial migratory species. Evolutionary Ecology 11: 505-517. (b) From Doligez B, Cadet C, Danchin E, and Boulinier T (2003) When to use public information for breeding habitat selection? The role of environmental predictability and density dependence. Animal Behaviour 66: 973-988.

Individuals may also use as information source their own experience and history, in particular their own performance in the activity considered in the habitat or patch, called personal information (and sometimes also private information, despite that other individuals can access it - Figure 9). In the context of foraging, different strategies involve gathering information via direct environment sampling by individuals, using in particular trial-and-error tactics (stay after success, leave after failure). Differences in timescale between foraging and breeding decisions imply that trial-and-error strategies, which can be optimal in foraging, are unlikely to be selected for alone in breeding habitat choice, because they would imply settling at random to breed and using only the breeding success achieved to decide about future habitat choice. This might be very costly when the total number of breeding attempts is limited, and personal information in the case of breeding habitat selection will often be mixed with other sources of information. Philopatry, that is, fidelity to the natal site, can be considered as a form of personal information use: individuals choose a site whose quality has allowed their own growth and survival.

Social cues

Conspecifics can also be used as a source of information about local habitat quality, that is, social information, because they share the same needs. Social information may be provided either intentionally through signals (communication), or inadvertently (inadvertent social information), when individuals monitor the behavior and performance of their conspecifics. When individuals use social information, they benefit in particular from environment sampling performed by others. Individuals can be expected to use social information more often for breeding than foraging habitat choice, and the importance of this information for breeding habitat choice has recently been emphasized (Figure 10).

Conspecifics' presence on a habitat patch as an information source has received much attention (social attraction process). It can reveal good enough conditions for a local population to persist (Figure 10). However, the mere presence of conspecifics may be misleading because the correlation between local density and habitat quality can prove weak in certain conditions. Conspecifics' activity and their success may better reveal habitat quality. Where conspecifics are the most successful can indicate where an individual is the most likely to be successful itself. Conspecific success integrates in a single parameter the effect of all components of environmental quality, including social interactions (Figure 10). It can also be more precise than personal information when based on large samples (e.g., many conspecifics), and when phenotype-environment interactions are limited. The

e se

SS 4S 3S 2S

IS s ee

Males Females

American robins (p = 0.006)

Males Females

Brown thrashers (p = 0.002)

Males Females

American robins (p = 0.006)

Males Females

Brown thrashers (p = 0.002)

Failure

Males

Females

Figure 9 Influence of personal information (individual's breeding success) in subsequent breeding habitat choice in (a) American robins (Turdus migratorius) and brown thrashers (Toxostoma rufum), and (b) collared flycatchers. Failed (naturally or experimentally) breeders are more likely to disperse to another patch in the following year compared to successful breeders. Individuals use their own reproductive performance as a cue to assess the current local breeding habitat quality and adjust their breeding patch choice in the next year. (a) Data from Haas CC (1998) Effects of prior nesting success on site fidelity and breeding dispersal: An experimental approach. Auk 115, 929-936. (b) From Doligez B, Danchin E, Clobert J, and Gustafsson L (1999) The use of conspecific reproductive success for breeding habitat selection in a non-colonial, hole-nesting species, the collared flycatcher. Journal of Animal Ecology 68: 1193-1206.

information derived from the performance of other individuals sharing ecological requirements has been called public information, in contrast to personal information.

The use of social information can be extended to heterospecifics, provided that they share the same needs (e.g., food or breeding sites), leading to interspecific social attraction or the use of heterospecific public information (Figure 10). Because their characteristics will slightly differ from individuals of the focal species, they could even provide additional information compared to conspecifics.

Individuals are likely to combine and use several information sources, in order to refine their assessment of local habitat quality and adjust their future decisions, depending on which factors affect fitness and relative costs of gathering each information (Figure 11).

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