Drivers of alloparental provisioning of fledglings in a colonially-breeding bird

Offspring provisioning represents a major reproductive cost. However, evidence suggests that parents sometimes feed unrelated offspring. Several hypotheses could explain this puzzling phenomenon. Adults could feed unrelated offspring that are (1) of close social associates to facilitate these juveniles’ integration into their social network (resulting in social inheritance), (2) potential extra-pair offspring, (3) at a similar developmental stage as their own, (4) coercing feeding by begging, or (5) less-developed and who’s enhanced survival would benefit the adult or its own offspring (the group augmentation hypothesis). Colonial breeders are ideal for investigating the relative importance of these hypotheses because offspring are often kept in crèches where adults can exhibit allofeeding. Using automated monitoring of replicated captive zebra finch (Taeniopygia guttata) colonies, we found that while parents selectively fed their own offspring, they also consistently fed unrelated offspring (32.48% of feeding events). Social relationships among adults prior to breeding did not predict allofeeding, nor was provisioning directed towards unrelated offspring directed to potential genetic offspring. Instead, adults preferentially fed less-developed non-offspring, despite these not begging more frequently than larger ones did. Our study suggests that allofeeding is consistent with group augmentation, which could be beneficial through colony maintenance or increased offspring survival.
Methods
dataChickID_toPublish20200223.csv: dataset containing the information about each chick.

dataParentsID.csv: dataset containing information about adults (parents).

dataQ.csv: dataset of observed feeding visits/events identified in the videos, including information of attendees and the occurrence of begging behaviour.

Event_All_Count.csv: dataset of observed feeding visits where parents fed non-offspring. This dataset was created by transforming “dataQ.csv” based on $EventID and the relationship of fed chicks (i.e. “unrelated” to the focal adult, $AdultID).

massChecksChicksCross-foster.csv: dataset for chick ID, body mass, and age (i.e. days old).

2018_AX_prebreedingMtx.RData: data on social interactions in each of the aviaries (1 to 4) during the pre-breeding period. These data were collected via an automated tracking system, 8-megapixel Camera Module V2 (RS Components Ltd and Allied Electronics Inc.) controlled by a Raspberry Pi3 Model B (Raspberry Pi Foundation), and individuals were identified by a backpack containing a 2D-tag (see Alarcón-Nieto et al 2018).

子代抚育是一项主要的繁殖成本。然而，已有研究证据表明，亲代有时会抚育非亲生子代。目前已有数种假说可解释这一令人费解的现象：成鸟可能会抚育以下几类非亲生子代：（1）亲密社交伙伴的幼崽，以帮助其融入自身社交网络（即社交继承假说）；（2）潜在的婚外子代；（3）与自身子代发育阶段相近的幼崽；（4）通过乞食行为胁迫亲代进行抚育的幼崽；（5）发育程度更低的幼崽——这类幼崽的存活率提升后，可使亲代自身或其亲生子代获益（即群体扩增假说）。

社群繁育者是验证上述假说相对重要性的理想研究模型，因为其子代常聚集于育幼群（crèche）中，亲代可在此开展异亲抚育（allofeeding）。本研究通过对重复设置的人工饲养斑胸草雀（Taeniopygia guttata）社群进行自动化监测，结果显示：尽管亲代会优先抚育亲生子代，但仍会持续对非亲生子代进行抚育（占总抚育行为的32.48%）。繁殖前成鸟间的社交关系无法预测异亲抚育行为，且亲代的抚育对象也并非潜在的遗传子代。与之相反，亲代会优先抚育发育程度更低的非亲生幼崽，尽管这类幼崽的乞食频率并未高于体型更大的幼崽。本研究表明，异亲抚育行为符合群体扩增假说，其可通过维持社群结构或提升子代存活率使亲代获益。

研究方法
dataChickID_toPublish20200223.csv：包含每只幼崽相关信息的数据集。
dataParentsID.csv：包含成鸟（亲代）相关信息的数据集。
dataQ.csv：从视频中识别得到的观察性抚育到访/事件数据集，包含参与抚育的个体信息以及乞食行为的发生情况。
Event_All_Count.csv：记录亲代抚育非亲生幼崽的观察性抚育到访数据集。该数据集通过以$EventID以及被抚育幼崽与目标成鸟$AdultID的亲缘关系（即"非亲生"）为依据，对"dataQ.csv"进行转换后得到。
massChecksChicksCross-foster.csv：包含幼崽ID、体重以及日龄信息的数据集。
2018_AX_prebreedingMtx.RData：包含繁殖前期4个笼舍（编号1至4）内成鸟社交互动情况的数据集。该数据集通过由树莓派3 Model B（Raspberry Pi Foundation）控制的800万像素摄像头模块V2（RS Components Ltd及Allied Electronics Inc.）组成的自动化追踪系统采集得到，个体识别依托搭载二维标签的背带完成（详见Alarcón-Nieto等人2018年的研究）。