Seed size, bill morphology, and handling time influence preferences for native vs. nonnative grass seeds in three declining sparrows

Titulaer, Mieke; Melgoza‐Castillo, Alicia; Macías‐Duarte, Alberto; Panjabi, Arvind O.

doi:10.1676/17-003.1

Cited by 13 publications

(13 citation statements)

References 44 publications

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“…Through morphological co‐adaptations of seeds and bills, birds with smaller bills could process small seeds faster than larger‐billed birds because of their greater dexterity in positioning small seeds in their bills for dehusking or cracking (Díaz 1990), and birds with larger bills could handle larger seeds faster than small‐billed species because they are able to apply greater pressure on the seeds (Grant 1986, van der Meij and Bout 2004). Thus, some bill sizes and morphologies can optimise the processing speed of some seeds (Ziswiler 1965, Grant 1986, Díaz 1990, 1996), and birds might prefer seeds that require less handling time (Willson and Harmeson 1973, Keating et al 1992, De Nagy Koves Hrabar and Perrin 2002, Carrillo et al 2007, Titulaer et al 2018a).…”

Section: Introductionmentioning

confidence: 99%

“…Certainly, birds could maximise their energy intake rate by optimising several possible combinations of handling time and energy reward, but the influence of each tactic remains little known because most studies address them one by one instead of trying to weigh their relative importance (Díaz 1996). Moreover, energy reward has sometimes been inferred indirectly by using the seed mass (Wang and Chen 2009, Titulaer et al 2018a, b) or the mass intake per unit of time (Schluter 1982, Pulliam 1985) as indicators of profitability. Although such assumptions are plausible, the hypothesis that birds maximise energy intake rate by choosing the seeds with a higher energy reward deserves direct testing.…”

Section: Introductionmentioning

confidence: 99%

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Plausible causes of seed preferences and diet composition in seed‐eating passerines

Marone

Cueto

Casenave

et al. 2021

Journal of Avian Biology

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We evaluated whether seed mass, handling time, handling efficiency and profitability account for (a) preferences in controlled experiments and (b) field‐diet composition of four bird species of the Monte desert, Argentina. The question of whether birds maximise their energy intake rates while feeding on seeds is assessed. We used feeding experiments with six native seed species of 0.07–0.75 mg (i.e. the seed‐size range consumed in nature), which account for 0.59–0.84 of the field diet of the four birds. We measured seed‐handling times and used published information on bird preferences and diets, and on seed chemistry, for further calculations. Bird preferences were always positively related to seed mass and also to seed profitability in the two intermediate‐sized birds. Diet composition correlated positively with seed mass and negatively with seed profitability in three species, but some birds also showed a flexible behaviour eating the most attractive seeds according to their availability. This behaviour is not genuinely opportunistic because it only focuses on a restricted fraction of the total seed species present in the field. Contrary to expectations of species coexistence due to resource partitioning, small and large birds showed similar feeding efficiencies when eating the smaller and the larger seeds. The positive association between seed mass and profitability in several studies suggests that most birds can maximise their energy reward, on average and in the long‐term, by preferring the larger seeds. A combination of potential feeding optimisation with certain flexibility in the field may characterise the feeding ecology of desert seed‐eating birds.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Plausible causes of seed preferences and diet composition in seed‐eating passerines

Marone

Cueto

Casenave

et al. 2021

Journal of Avian Biology

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“…Existing research on grassland birds has been heavily biased toward breeding season abundance/occupancy and nesting success ( Muller et al 2021 ). Only a handful of studies have been conducted on aspects of grassland bird wintering ecology including work on survival ( Thatcher et al 2006 ;Macías-Duarte et al 2017 ;Pérez-Ordoñez et al 2022 ), habitat use ( Marx et al 2008 ;Macías-Duarte et al 2009 ;Macías-Duarte and Panjabi 2013 ;Muller et al 2018 ;Alfaro et al 2019 ;Strasser et al 2019 ;Franco et al 2022 ), and diet ( Renfrew et al 2017 ;Titulaer et al 2017Titulaer et al , 2018Olalla-Kerstupp et al 2020 ;Guerrero et al 2022 ). Further, most existing studies on the topic have been conducted on mixed-grass prairie songbirds, leaving many species virtually unstudied during this period.…”

Section: Knowledge Gaps and Future Directionsmentioning

confidence: 99%

Review of Conservation Challenges and Possible Solutions for Grassland Birds of the North American Great Plains

Bernath-Plaisted,

Correll,

Somershoe

et al. 2023

Rangeland Ecology & Management

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“…Like pre‐dispersal loss, the loss of dispersed seeds to herbivores can be high (Capon and O'Connor, 1990 ; Reed et al, 2004 ; Schöning et al, 2004 ). Awns may deter herbivores by increasing the time they spend handling the seeds (Schöning et al, 2004 ; Titulaer et al, 2018 ). Seed preference of sparrows around Chihuahua, Mexico varied considerably among six species of grass: Bouteloua gracilis , B. curtipendula , Leptochloa dubia (= Disakisperma dubium ), Melinis repens , Eragrostis lehmanniana , and Pennisetum ciliare (= Cenchrus ciliaris ), comprising three native and three exotic grasses, respectively (Titulaer et al, 2018 ).…”

Section: Possible Functions Of Awnsmentioning

confidence: 99%

Diverse ecological functions and the convergent evolution of grass awns

Petersen

Kellogg

2022

American J of Botany

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The awn of grasses is a long, conspicuous outgrowth of the floral bracts in a grass spikelet. It is known to impact agricultural yield, but we know little about its broader ecological function, nor the selective forces that lead to its evolution. Grass awns are phenotypically diverse across the extant ~12,000 species of Poaceae. Awns have been lost and gained repeatedly over evolutionary time, between and within lineages, suggesting that they could be under selection and might provide adaptive benefit in some environments. Despite the phylogenetic context, we know of no studies that have tested whether the origin of awns correlates with putative selective forces on their form and function. Presence or absence of awns is not plastic; rather, heritability is high. The awns of grasses often are suggested as adaptations for dispersal, and most experimental work has been aimed at testing this hypothesis. Proposed dispersal functions include soil burial, epizoochory, and aerial orientation. Awns may also protect the seed from drought, herbivores, or fire by helping it become buried in soil. We do not fully understand the fitness or nutrient costs of awn production, but in some species awns function in photosynthesis, providing carbon to the seed. Here we show that awns likely provide an adaptive advantage, but argue that studies on awn function have lacked critical phylogenetic information to demonstrate adaptive convergent evolution, are taxonomically biased, and often lack clear alternative hypotheses.

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Seed size, bill morphology, and handling time influence preferences for native vs. nonnative grass seeds in three declining sparrows

Cited by 13 publications

References 44 publications

Plausible causes of seed preferences and diet composition in seed‐eating passerines

Plausible causes of seed preferences and diet composition in seed‐eating passerines

Review of Conservation Challenges and Possible Solutions for Grassland Birds of the North American Great Plains

Diverse ecological functions and the convergent evolution of grass awns

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