Elena Álvarez

Nest Quality in Relation to Adult Bird Condition and Its Impact on Reproduction in Great Tits Parus major

Abstract. n Birds nests are special structures built with reproductive aims. Size and structure of the nest can arise from evolutionary trade-offs between benefits such as the insulation from unfavourable conditions, maintenance of eggs or chicks, or security against predation, and costs such as energy spent in construction of the nest and the risk of predation in more visible nests. Therefore, building a good nest is beneficial in terms of reproductive output but expensive in terms of time and energy, so probably only “good” parents would be able to build “good” nests. Our objective was to study possible relationships between the quality of the parents and the quality of the nest, and between the quality of the nest and breeding performance in a Great Tit Parus major population. We found positive relationships between different components of the nest quality and components of breeding performance. However, we did not find any significant relationship between quality of the parents and that of the nest. A weak, though significant positive correlation was found between female size and breeding success rate.

Variation in Great Tit nest mass and composition and its breeding consequences: a comparative study in four Mediterranean habitats

Bird nests are structures whose properties affect breeding performance. Thus, the vast majority of bird species build their own characteristic nests, selecting appropriate materials to do so. However, in habitats where the availability of “ideal” materials is low, some ability to use alternative ones would be necessary, even at the cost of having breeding success reduced. The Great Tit (Parus major) breeds under widely different environmental conditions. Its nests are althought to be composed mainly of moss, although very few studies have quantified nest composition. Our target here was describing Great Tit nest mass and composition in four different Mediterranean habitats, and exploring their fitness consequences. We recorded the basic breeding parameters, collected nests after fledging, and decomposed a sample of them, in four eastern Spanish populations: Pina (pines and oaks), Mariola (pines), Font Roja (holm oaks), and Sagunto (orange trees). Nests were heavier in Sagunto and Mariola and lighter in Font Roja, and those from Sagunto had the lowest amount of moss. Clutch size decreased as moss mass increased in the four sites. In Sagunto, hatching success increased as moss mass increased. In all habitats, nestling condition was lower when the amount of sticks and feathers was higher. We conclude that Great Tit nest mass and composition varies considerably between habitats, and the amount of different materials could affect different breeding parameters.

Nest Characteristics and Reproductive Performance in Great Tits Parus major

Summary. n Nest characteristics and breeding performance in great tits Parus major. For birds, building a nest entails a number of costs but it confers important benefits, so that nest quality is often positively associated with reproductive performance. Our main objective was to study the relationships between nest characteristics and breeding performance, and the possible between-year variability in these relationships. We used great tits Parus major as the model species and studied a population breeding in nestboxes within orange plantations in eastern Spain. The study only considered first clutches, in two consecutive years. Nests were visited as frequently as necessary to record basic breeding parameters. We measured and weighed all nests during the incubation period, took biometric characteristics of parents and nestlings (tarsus length, weight and condition, and parental wing length) and measured the immune response of chicks (phytohemagglutinin test). We used principal component analysis to reduce the number of nest variables to three relevant components. Overall, 2007 seemed to have been a more favourable year, with larger clutch sizes and heavier fledglings produced than in 2006. Laying date was earlier in nests with larger nest cup diameter, hatching success was higher as relative cup depth increased in 2007, and fledging success increased as overall nest size increased in 2007. The only significant relationship between parental traits and nest characteristics was that first year females built deeper nests than older ones. Females with longer tarsi and in poorer physical condition started laying earlier. Increased fledging success was associated with decreasing male tarsus length and fledgling condition was better in nests attended by older males. In general, nest characteristics were positively related to breeding success, although specific relationships between the different components could vary between years. These relationships have been more evident in a trophically “good” year than in a “bad” one.

Within and between population variations of incubation rhythm of great tits Parus major

Uniparental incubation frequently means that eggs remain unattended for periods where the incubating bird is foraging out of the nest. The determination of incubation rhythms (i.e., the length and temporal pattern of incubation sessions) and the factors which affect them are therefore important to understand life-history trade-offs. We described the incubation rhythm and its temporal variation of a southern European great tit Parus major population, and review previous studies to check for latitudinal trends. In the studied population, females were active (from first exit in the morning to last entrance in the evening) 12.5 h per day, performing incubation sessions (on-bouts) of 26 min and recesses (off-bouts) of 12 min. Thus, they were incubating around 67% of their active day, or 83% of the whole day. Attentiveness (% of time incubating) increased throughout the incubation period, due to shorter off-bouts. The active day was longer as the number of daylight hours increased. We show for the first time in a bird species that attentiveness was constant along a latitudinal gradient ranging from Norway to Spain. Females spend a higher proportion of the daylight hours out of the nest as latitude decreases, compensating incubation time during the longer nights. Off-bouts were shorter in central European populations, increasing towards the north and the south, while on-bouts showed no latitudinal variation.

A recipe for postfledging survival in great tits Parus major: be large and be early (but not too much)

Abstract Survival of juveniles during the postfledging period can be markedly low, which may have major consequences on avian population dynamics. Knowing which factors operating during the nesting phase affect postfledging survival is crucial to understand avian breeding strategies. We aimed to obtain a robust set of predictors of postfledging local survival using the great tit (Parus major) as a model species. We used mark–recapture models to analyze the effect of hatching date, temperatures experienced during the nestling period, fledging size and body mass on first‐year postfledging survival probability of great tit juveniles. We used data from 5192 nestlings of first clutches ringed between 1993 and 2010. Mean first‐year postfledging survival probability was 15.2%, and it was lower for smaller individuals, as well as for those born in either very early or late broods. Our results stress the importance of choosing an optimum hatching period, and raising large chicks to increase first‐year local survival probability in the studied population.

Incubation and hatching periods in a Mediterranean Great Tit Parus major population

Capsule The onset of incubation relative to clutch completion is highly variable in Great Tits Parus major, and has important consequences for the duration of the incubation and hatching periods. Aim To investigate when incubation starts relative to clutch completion, its effects on the length of the incubation and hatching periods, and which proximate factors affect all of these traits. Methods We used data from a Great Tit population in Eastern Spain collected over 15 years. Periodic visits to the nests (daily at some stages) allowed the determination of breeding parameters of interest. General linear models were used for analyses. Results On average, incubation started the day of laying of the last egg and lasted 13.2 days. The hatching period lasted 1.7 days. Incubation started earlier relative to clutch completion as temperatures during the laying period were higher and as clutch size increased. The incubation period was shorter if incubation started later relative to clutch completion. Hatching asynchrony increased as incubation started earlier relative to clutch completion and as the incubation period decreased. Conclusions The onset of incubation relative to clutch completion is highly variable, and has important consequences for the duration of the incubation and hatching periods. Starting incubation before or after clutch completion could, respectively, advance or delay the hatching date, although advancement would be at the cost of increasing the degree of hatching asynchrony.

Nest insulating capacity during incubation and after fledging are related

Most birds build nests to hold eggs and nestlings. An important property of nests is their ability to keep eggs and nestlings at an optimum temperature. This is usually measured as the insulating capacity (IC); nests with a higher IC will keep their content warm for longer. The usual protocol to estimate IC involves collecting nests after fledging of the young. However, nest properties change throughout the nesting period, potentially affecting IC. Therefore, a relevant question is whether the nest IC, measured after fledging, actually reflects its IC during incubation and early nestling development, when it is most crucial. In April 2015, we collected 18 Great Tit (Parus major) nests 3-4 days after incubation had started, measured their fresh mass and IC, and returned them to the nestboxes. We collected these same nests again after fledging, and measured their IC and fresh and dry masses. IC tended to be lower after fledging than during incubation, but both measures were correlated. Fresh nest mass was higher after fledging than during incubation, and dry nest mass was correlated to both fresh masses. Nest mass gained between incubation and fledging was positively related to clutch size. As expected, nest mass increased throughout the nesting period, but the deterioration of nest structure as the nestlings grew up tended to negatively affect its IC. However, the correlation between IC in the two nesting stages allows the use of post-fledging nests for comparative studies of nest insulating capacity.