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Behavioral research often involves capturing and video-recording birds, but these procedures may have undesired effects on the behavior of birds that have rarely been quantified. In addition, birds in urban and more natural areas may differ in their sensitivity to disturbance. We examined the possible effects of both capturing, weighing and measuring, and taking a blood sample, and the presence of video-cameras on the behavior of male and female Great Tits (Parus major) breeding in urban and forest habitats. Using a 2 × 2 block design, we compared the behavior and breeding success of parents that either were or were not captured on their nests a few days before behavioral observations, and of parents that either were or were not habituated to the presence of a concealed video-recorder mounted on nest boxes. We found no significant effects of habituation to the camera on bird behavior, but males captured in their nest boxes were more vigilant and hesitated longer before entering nest boxes, and also had slightly lower provisioning rates than males that had not been captured. Captured females also tended to be more vigilant than females that had not been captured, but their provisioning rates were not affected. Capturing males also influenced the behavior of their non-captured mates, but capturing females had no effect on the behavior of their non-captured mates. We found no difference in the effects of capture on Great Tits in urban and forest habitats, and our treatments also had no effect on the mass, size, and survival of nestlings until fledging. Our results suggest that, for Great Tits, being captured results in sex-dependent behavioral effects that can last for at least several days. As such, we suggest that the possibility of similar effects in other species of birds should be considered in behavioral studies where birds must be captured, and recommend either that behavioral data be collected before capturing birds or that all birds in a study should be captured and handled in a standardized way. Efecto de la captura y la toma de videos en la conducta y éxito reproductivo de Parus major en hábitats urbanos y naturales Los estudios de conducta muchas veces incluyen la captura y la toma de video de aves. Pero estos procedimientos pudieran tener efectos, no deseados, en la conducta de las aves que raras veces es cuantificado. Además las aves en hábitats urbanos y áreas más naturales pudieran diferir en su susceptibilidad al disturbio. Examinamos el posible efecto de la captura, pesaje, toma de medidas y de muestras de sangre y la presencia de cámaras de video en la conducta de hembras y machos de Parus major, reproduciéndose en hábitats urbanos y naturales. Utilizando un diseño de “bloque” 2 × 2, comparamos la conducta y el éxito reproductivo de individuos que eran capturados o no capturados en sus nidos días antes de llevarse a cabo observaciones de conducta, y de individuos que estaban o no estaban habituados a la presencia de cámaras de video escondidas, pero montadas, en cajas de anidamiento. Encontramos que no hubo efecto significativo en la conducta de las aves habituadas a la cámara. Sin embargo los machos capturados en la caja donde anidaban fueron más cuidadosos y precavidos para entrar en sus cajas. Además se redujo, ligeramente, el número de viajes para llevar comida al nido, en comparación con machos que no fueron capturados. Las hembras capturadas también fueron más precavidas que las no capturadas, pero su tasa de llevar alimentos a los pichones no fue afectada. La captura de los machos también influyó en la conducta de su pareja, que no fue capturada, aunque no hubo efecto en la conducta, de la pareja, en hembras capturadas. No encontramos diferencias en el efecto de la captura de estas aves en ambientes urbanos y forestados. Nuestra manipulación no tuvo efecto en la masa, tamaño y sobrevivencia de los pichones hasta el momento de dejar el nido. Los resultados sugieren que el efecto de la captura, en la conducta de Parus major, depende del sexo del ave y que dicha conducta puede durar por varios días. A tales efectos advertimos que existe la posibilidad de efectos similares en otras especies de aves que debe considerarse en estudios de conducta en donde las aves sean capturadas. Recomendamos que los datos sobre conducta sean tomados previos a la captura de las aves, o que todas las aves en el estudio sean capturadas y manejadas en una forma estandarizada. Fig. S1. (A) The video camera and the dummy camera. (B) Column 1, front view: the video camera and the dummy camera, respectively, hidden in the plastic box for concealment, and the plastic box attached emptily to the nest box. Column 2, back view: the plastic box with the camera and the dummy camera, respectively, and attached emptily to the nest box. Table S1. Initial full linear mixed-effects models of (A) males' and (B) females' hesitation behavior, vigilance and chick-feeding rate, and (C) parents' total chick-feeding rate (where a pair's capture status was “yes” if one of the parents was captured and “no” if none of them were captured). Table S2. Initial linear mixed-effects models of the effects of partner's capture status on non-captured (A) males' and (B) females' behavior. Table S3. Initial linear mixed-effects models of the effects of capture and camera-habituation on nestlings' body mass, tarsus length and wing length, using the capture status of (A) males, (B) females and (C) at the pair level (i.e., one or none of the parents captured). Table S4. Final linear mixed-effects models of the effects of capture and camera-habituation on hesitation behavior, vigilance and chick-feeding rate of (A) males and (B) females, using “capture treatment” as a three-level variable to describe birds' nest-trapping experience: “never captured”, “captured in previous years” (but not in the present breeding season), “captured in the present study” (i.e., in the present breeding season). Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.