DOI: 10.5061/dryad.cjsxksng3
title: Morphometric variation and deteriorating food availability both explain seasonally declining reproductive success of Dicrurus hottentottus (Hair-crested Drongo)

description: Seasonally declining reproductive performance in avian
 populations may be attributed to high-quality
 individuals breeding earlier than low-quality individuals (the
 ‘quality hypothesis’), to deteriorating environmental conditions
 (the ‘date hypothesis’), or both. By comparing the
 reproductive performance among different perennial pairs, and the
 same perennial pairs across different years, we tested
 the influence of timing of breeding on reproductive performance
 in the Hair-crested Drongos (Dicrurus hottentottus) from
 2010 to 2022. Breeding pairs that typically
 laid earlier relative to the population mean (i.e.,
 early-breeding pairs) exhibited a significantly
 higher fledging rate compared to breeding pairs
 that often bred later relative to the population mean
 (i.e., late-breeding pairs). For a given pair, the fledging rate of
 early-breeding pairs increased when they bred later compared to
 other years, while the fledging rates of
 late-breeding pairs were significantly lower in years
 when they bred later than usual. We found that male
 morphological traits were associated with both the timing of
 breeding and the feeding rate. Pairs with
 long-billed (indicator of high
 quality) males bred earlier than pairs with
 short-billed males, and pairs with larger
 males (indicator of high quality) had a higher feeding
 rate than pairs with smaller males. Female age had reversed effects on the
 timing of breeding and fledging rate: older
 females tended to breed earlier than younger females; but there
 was a sharp decline in fledging rate after 7 years of age in late-breeding
 pairs. Finally, our results showed that the feeding rate and the
 amount of invertebrate biomass decreased with laying date,
 indicating deteriorating feeding conditions later in the breeding
 season. Overall, our findings support both the ‘quality hypothesis’ and
 the ‘date hypothesis’. Low-quality Hair-crested Drongos are likely to be
 most adversely affected by the phenological mismatches induced by climate
 change, which, in turn, may affect population dynamics through reduced
 fecundity.
description: We collected all the data from the field. We used the within
 subject model to test whether the 'individual quality
 hypothesis' or 'the date hypothesis' could explain the
 seasonal declining of the breeding performance.
description: # Morphometric variation and deteriorating food availability both explain
 seasonally declining reproductive success of Dicrurus hottentottus
 (Hair-crested Drongo)
 [https://doi.org/10.5061/dryad.cjsxksng3](https://doi.org/10.5061/dryad.cjsxksng3) There were three parts of analyses in this paper. The first part was between and within-subject analysis, which could distinguish the effects of between individuals (quality hypothesis) and within individual effects (date hypothesis) (Perennial_pair.csv).  The second part was to analyze how parents' quality affected laying date and fledging rate. The last part was to analyze the variation of food resource during the breeding season (Feeding_rate.csv and feeding_rate_2022.csv). ## Description of the data and file structure **Perennial pairs.csv** was the data used for most of the analysis, such as the variation of the fledging rate, within-subject analysis, et al.   Empty cells in numeric columns indicate missing values (e.g., data not collected). | **Variables** | **Definition** | | :------------------------------------ | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | PairID | The unique ID of each breeding pairs | | Year | The breeding year | | Laying-origin | Absolute laying date: The calendar laying date of each nest; expressed as the number of days between the laying date of each nest and May 1 | | cfledging rate | The ratio between the number of fledglings and the clutch size for each brood. Same as Fledging rate. | | Bodymass.f.mean | The mean body mass (g) of each female | | Agef | Age of female (year) | | Agem | Age of male (year) | | Duration | The number of bonded years for each breeding pair of this year | | Fate | The fate of each brood (success:1 or not:0) | | Total duration | The total number of bonded years for each breeding pair  | | Laying\_median (Relative laying date) | The difference between laying dates of each breeding pair and the population median laying date in each year (i.e., negative values indicated earlier and positive values indicated later than the population median | | Mean laying date\_median | Media laying date of each breeding pair during the study perid | | Difference\_median | The difference between relative laying date of a given fpair in a given year and the mean laying date of that pair. | | Stage\_median | We categorized pairs as early-breeding if their mean laying date was below zero,  late-breeding if above zero, and middle-breeding if exactly zero. | | PC1.F | The variables of main contribution are Tail length, Body length, Wing length. See in Supplemental materials (Figure S4). | | PC2.F | The variables of main contribution are Tarsus length and Bill length. See in Supplemental materials (Figure S4). | | PC3.M | The variables of main contribution are Tail length, Body length, and Wing length. See in Supplemental materials (Figure S5). | | PC1.M | The variable of main contribution is Tarsus length. See in Supplemental materials (Figure S5). | | PC2.M | The variable of main contribution is Bill length. See in Supplemental materials (Figure S5). | | Breeding experience | The breeding experience of male: 1 means have breeding experience; 2 means without breeding experience; 3 means not sure | **Feeding rate.csv** and Feeding rate-2022 were the data for feeding rate of drongos for 2010-2022 and insect biomass in 2022. Empty cells in numeric columns indicate missing values (e.g., data not collected). | Variables | Definition | | :---------------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | PairID | The unique ID of each breeding pairs | | Year | The breeding year | | Day relative to June 1st | The calendar laying date of each nest; expressed as the number of days between the laying date of each nest and June 1 | | Age.F | Age of female (year) | | Age.M | Age of male (year) | | T-used ratio | The occupied ratio of each territory | | Insect mass-2022 | The insect mass (g) collected in 2022; the average bio mass from the 10 days preceding the recording of the feeding rate | | Video Age | The nest age (from the day of the first egg hatched) when record the video | | Feeding rate-nest | The feeding frequency (Number of feeding visits) to the nest of each nest per hour | | Feeding rate-nestlings | The feeding frequency (Number of feeding visits) of each nestling per hour | | Num.of Nestlings | The number of nestlings in each brood | | Monitor.years.f | The total monitor years of female | | Monitor.years.m | The total monitor years of male | | Fate | The fate of each brood | | Breeding.experience | The breeding experience of male: 1 means have breeding experience; 2 means without breeding experience; 3 means not sure | | Laying.media (Relative laying date) | The difference between laying dates of each breeding pair and the population median laying date in each year (i.e., negative values indicated earlier and positive values indicated later than the population median | **Feeding rate-2022.csv** | **Variables** | **Definition** | | :--------------------- | :----------------------------------------------------------------------------------------------------------------------- | | Pair ID | The unique ID of each breeding pairs | | Day from May 1st | The calendar laying date of each nest; expressed as the number of days between the laying date of each nest and May 1. | | Brood size | The successful number of hatched nestlings in each nest | | Feeding rate\_nest | The feeding frequency (Number of feeding visits) to the nest of each nest per hour | | Feeding rate\_nestling | The feeding frequency (Number of feeding visits) of each nestling per hour | | Insect AVE-10 | The insect mass (g) collected in 2022; the average bio mass from the 10 days preceding the recording of the feeding rate |