198 The Condor 115(1):198–208  The Cooper Ornithological Society 2013 1 E-mail: yasukawa@beloit.edu Manuscript received 6 September 2011; accepted 2 July 2012. The Condor, Vol. 115, Number 1, pages 198–208. ISSN 0010-5422, electronic ISSN 1938-5422.  2013 by The Cooper Ornithological Society. All rights reserved. Please direct all requests for permission to photocopy or reproduce article content through the University of California Press’s Rights and Permissions website, http://www.ucpressjournals.com/ reprintInfo.asp. DOI: 10.1525/cond.2012.110144 INTRODUCTION In animals with parental care, communication between par- ents and offspring is critical (Clutton-Brock 1991). Birds have been the subjects of many studies of parent–offspring commu- nication, and many of these studies have focused on nestlings’ begging (Kilner and Johnstone 1997, Budden and Wright 2001, Wright and Leonard 2002). When a parent arrives at the nest with food, nestlings use postures, movement, and vocal- izations, display their colorful gapes, and jostle for position (Kilner 2002) to beg (Budden and Wright 2001, Wright and Leonard 2002), but when the parent controls allocation within the brood, it must assess many behavioral, physiological, and morphological traits when deciding which nestling to feed (Budden and Wright 2001, Clark 2002, Mock et al. 2011). We investigate two related but not identical questions about pa- rental allocation of care. What does begging signal? On what do parents base their allocation decisions? Clark (2002) divided the signal components of nestlings’ begging into three categories: hunger, need, and condition. Mock et al. (2011) discussed these categories by suggest- ing that parent-in-control hypotheses for nestlings’ begging could be divided into three types. The signal-of-hunger (SoH) hypothesis proposes that volitional begging signals act like a fuel gauge (Grodzinski and Lotem 2007) to express a nest- ling’s fullness. The signal-of-need (SoN) hypothesis sug- gests that parents use begging signals to assess how much a food item will improve the signaler’s fitness, allowing par- ents to favor needy offspring (Godfray 1991, 1995). Finally, according to the signal-of-quality (SoQ) hypothesis, begging HOW DO FEMALE RED-WINGED BLACKBIRDS ALLOCATE FOOD WITHIN BROODS? NICOLE KRAUSS AND KEN YASUKAWA 1 Beloit College, Department of Biology, Beloit, WI 53511 Abstract. Nestlings communicate with parents via begging, but what does begging signal and how do parents allocate food to their nestlings? We tested the signal-of-need (SoN) and signal-of-quality (SoQ) hypotheses for nestling begging in the Red-winged Blackbird (Agelaius phoeniceus) by attempting to determine whether begging is negatively (SoN) or positively (SoQ) condition dependent, and by attempting to identify the attributes of nest- lings that parents use to allocate food within broods. We quantified begging by its mean intensity (scale 0–7) and mean duration and parental allocation by the number of times each nestling was fed. We found that the intensity and duration of begging were not correlated with nestlings’ size (estimated by body mass and tarsus length), condition (estimated from the residual of mass regressed on tarsus length), age, sex, or testosterone concentration, so begging did not appear to be negatively or positively condition dependent. A generalized linear model showed that mean intensity of begging, body condition, and log testosterone concentration were significant predictors of the number of feedings. These results are consistent with parents using begging intensity and nestling quality, but not long-term need, to allocate food within broods. Key words: Agelaius phoeniceus, begging, condition, hunger, need, quality, Red-winged Blackbird. ¿Cómo Asignan los Alimentos entre las Crías las Hembras de Agelaius phoeniceus? Resumen. Los pichones mendigan para comunicarse con sus padres, pero ¿qué señal representa esto y cómo los padres asignan los alimentos a sus pichones? Evaluamos las hipótesis de la señal de necesidad (SdN) y la señal de calidad (SdC) para pichones de Agelaius phoeniceus que mendigan intentando determinar si la mendicidad depende negativa (SdN) o positivamente (SdC) de la condición, e intentando identificar los atributos de los pichones que usan los padres para asignar los alimentos entre las crías. Cuantificamos la mendicidad de acuerdo a su intensidad media (escala 0–7) y duración media, y la asignación de los padres con el número de veces que cada pichón fue alimentado. Encontramos que la intensidad y la duración de la mendicidad no estuvieron correlaciona- dos con el tamaño del pichón (estimado por la masa corporal y el largo del tarso), la condición (estimado a partir del residuo de la regresión de la masa con el largo del tarso), la edad, el sexo o la concentración de testosterona, por lo que la mendicidad no parece depender positiva o negativamente de la condición. Un modelo lineal generalizado mostró que la intensidad media de la mendicidad, la condición del cuerpo y la concentración logarítmica de la testosterona predijeron significativamente el número de provisiones de alimento. Estos resultados son consistentes con la noción de que los padres usan la intensidad de mendicidad y la calidad del pichón, pero no la necesidad de largo plazo, para asignar los alimentos entre las crías.