Site- and species-specific fuel load of European–Afrotropical passerines on arrival at three oases of southeast Morocco during spring migration

Abstract Background Crossing open water instead of following the coast(line) is one way for landbirds to continue migration. However, depending on prevailing weather and the birds’ physiological conditions, it is also a risky choice. To date, the question remains as to which interplay between environmental and physiological conditions force landbirds to stop on remote islands. We hypothesise that unfavourable winds affect lean birds with low energy resources, while poor visibility affects all birds regardless of their fuel loads. Methods To test this hypothesis, we caught 1312 common blackbirds Turdus merula stopping over on Helgoland during autumn and spring migration. Arrival fuel load was measured using quantitative magnetic resonance technology. Weather parameters (wind and relative humidity as a proxy for visibility) were interpolated for the night before arrival. Further, we calculated whether caught individuals would have successfully crossed the North Sea instead of landing on Helgoland, depending on wind conditions. Results Both wind and relative humidity the night before arrival were correlated with arrival fuel load. After nights with strong headwinds, birds caught the following day were mostly lean, most of which would not have managed to cross the sea if they had not stopped on Helgoland. In contrast, fat birds that could have successfully travelled on were caught mainly after nights with high relative humidity (≥ 80%). Furthermore, the rate of presumably successful flights was lower due to wind: although only 9% of all blackbirds captured on Helgoland had insufficient fuel loads to allow safe onward migration in still air, real wind conditions would have prevented 30% of birds from successfully crossing the sea during autumn and 21% during spring migration. Conclusions We were able to decipher how physiological condition, wind and relative humidity partially force blackbirds to stop on a remote island. Adverse winds tend to affect lean birds with low energy resources, while poor visibility can affect blackbirds, regardless of whether the arrival fuel load was sufficient for onward flight. Our findings will help to understand different migratory strategies and explain further questions like migration timing.

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Estimating Fuel Loads and Structural Characteristics of Shrub Communities by Using Terrestrial Laser Scanning

Remote Sensing ◽

10.3390/rs12223704 ◽

2020 ◽

Vol 12 (22) ◽

pp. 3704

Author(s):

Cecilia Alonso-Rego ◽

Stéfano Arellano-Pérez ◽

Carlos Cabo ◽

Celestino Ordoñez ◽

Juan Gabriel Álvarez-González ◽

...

Keyword(s):

Laser Scanning ◽

Goodness Of Fit ◽

Fire Hazard ◽

Structural Characteristics ◽

Fire Behavior ◽

Terrestrial Laser Scanning ◽

Fuel Load ◽

Fuel Loads ◽

Litter Depth ◽

Species Specific

Forest fuel loads and structural characteristics strongly affect fire behavior, regulating the rate of spread, fireline intensity, and flame length. Accurate fuel characterization, including disaggregation of the fuel load by size classes, is therefore essential to obtain reliable predictions from fire behavior simulators and to support decision-making in fuel management and fire hazard prediction. A total of 55 sample plots of four of the main non-tree covered shrub communities in NW Spain were non-destructively sampled to estimate litter depth and shrub cover and height for species. Fuel loads were estimated from species-specific equations. Moreover, a single terrestrial laser scanning (TLS) scan was collected in each sample plot and features related to the vertical and horizontal distribution of the cloud points were calculated. Two alternative approaches for estimating size-disaggregated fuel loads and live/dead fractions from TLS data were compared: (i) a two-steps indirect estimation approach (IE) based on fitting three equations to estimate shrub height and cover and litter depth from TLS data and then use those estimates as inputs of the existing species-specific fuel load equations by size fractions based on these three variables; and (ii) a direct estimation approach (DE), consisting of fitting seven equations, one for each fuel fraction, to relate the fuel load estimates to TLS data. Overall, the direct approach produced more balanced goodness-of-fit statistics for the seven fractions considered jointly, suggesting that it performed better than the indirect approach, with equations explaining more than 80% of the observed variability for all species and fractions, except the litter loads.

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A Novel Locality for the Observation of Thousands of Passerine Birds during Spring Migration in Los Angeles County, California

Western Birds ◽

10.21199/wb52.4.4 ◽

2021 ◽

Vol 52 (4) ◽

pp. 322-339

Author(s):

Ryan S. Terrill ◽

Christine A. Dean ◽

John Garrett ◽

Daniel J. Maxwell ◽

Lauren Hill ◽

...

Keyword(s):

Los Angeles ◽

Los Angeles County ◽

Pacific Coast ◽

Spring Migration ◽

Passerine Birds ◽

San Gabriel Mountains ◽

Species Migration ◽

The Pacific ◽

Migration Phenology ◽

Species Specific

Avian migration is a spectacular phenomenon, representing the annual movements of billions of birds globally. Because the greatest diversity and numbers of birds migrate at night, opportunities to observe active migration are rare. At a number of localities in North America, however, observers can quantify movements of many typically nocturnal migrants during daylight where they continue after dawn. Such locations have provided much information about species-specific phenology, status, and orientation during migration. Localities where morning flights of land birds can be observed are unevenly distributed, however, and are little reported along the Pacific coast. Here we describe a novel location for the observation of spectacular morning flights of nocturnal migrants during spring migration at Bear Divide, in the western San Gabriel Mountains, Los Angeles County, California. In two years of informal surveys at the site, we have recorded at least one morning with an estimated ~13,500 individual birds passing. Our preliminary analyses suggest that the peak of a species’ migration at Bear Divide is correlated with the latitude of a species’ breeding, being later in the spring as that latitude increases. Our data from Bear Divide provide an independent perspective on migration as quantified by local radar. Further work at this locality may help inform our knowledge of migration phenology and population trends.

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Flexibility and Control of Circadian Activity, Migratory Restlessness and Fueling in Two Songbird Migrants

Frontiers in Ecology and Evolution ◽

10.3389/fevo.2021.666176 ◽

2021 ◽

Vol 9 ◽

Author(s):

Susanne Åkesson ◽

Mihaela Ilieva ◽

Giuseppe Bianco

Keyword(s):

Fuel Load ◽

Time Shift ◽

Limited Attention ◽

Control Group ◽

Migratory Restlessness ◽

Migratory Activity ◽

Natural Photoperiod ◽

Timing Of Migration ◽

Species Specific ◽

Flexible Component

Juvenile songbirds rely on an endogenous program, encoding direction, distance, fueling, and timing of migration. Migratory distance is species-specific, expressed as a period of migratory restlessness, for which the length is correlated with distance, while fueling is modified to meet anticipated flight distances controlled by geomagnetic cues and amount of day-light available for foraging. How daylength affect onset and level of migratory activity and fueling decisions in wild birds have so far received limited attention. Here we study how photoperiod controls onset, level and extent of autumn migratory activity and fueling in juvenile diurnally migrating dunnocks, and nocturnally migrating European robins by experimentally increasing daylength. For both species, we kept a control group indoors at the location of capture in southern Sweden exposed to the natural photoperiod, and an experimental group with increased and advanced photoperiod by 2 h in the morning. Dunnocks initiated migratory activity at sunrise (or artificial sunrise) in both groups, demonstrating a highly responsive and flexible component for the onset of migration triggered by light. Experimental robins anticipated the end of nocturnal migratory activity predicting the earlier sunrise immediately after the time-shift and expressed this behavior already under darkness, supporting a fast-resetting mechanism to the new diel period. Timing of end of morning activity was not affected by the earlier sunrise in both species, suggesting a fixed endogenous control that persisted throughout the 13-day study period. Experimental dunnocks expressed higher overall activity and lower fuel loads than controls, while robins did not change their overall activity and fuel load in response to the shifted and increased photoperiod. These results reveal important adaptations for circadian timekeeping including both a flexible onset open to fast modifications and a more rigid end, with differential effects by the treatment on migratory activity and fueling in the two species.

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Days to Visit an Offshore Island: Effect of Weather Conditions on Arrival Fuel Load and Potential Flight Range for Common Blackbirds Turdus Merula Migrating Over the North Sea

10.21203/rs.3.rs-695821/v1 ◽

2021 ◽

Author(s):

Natalie Kelsey ◽

Ommo Hüppop ◽

Franz Bairlein

Keyword(s):

Relative Humidity ◽

North Sea ◽

Physiological Condition ◽

Spring Migration ◽

Low Energy ◽

Energy Resources ◽

Fuel Load ◽

Turdus Merula ◽

The North ◽

The North Sea

Abstract Background: Crossing open water instead of following the coast(line) is one way for landbirds to continue migration. However, depending on prevailing weather and the birds’ physiological condition, it is also a risky choice. To date, the question remains as to which interplay between environmental conditions and physiological condition force landbirds to stop on remote islands. We hypothesise that unfavourable winds would affect lean birds with low energy resources, while poor visibility would affect all birds regardless of their fuel load. Methods: To test this hypothesis, we used data of 1312 Common Blackbirds Turdus merula, caught while stopping over on Helgoland during autumn and spring migration. Arrival fuel load was measured using quantitative magnetic resonance technology. Weather parameters (wind and relative humidity as a proxy for visibility) were interpolated for the night before arrival. Further, we calculated whether caught individuals would have managed to successfully cross the North Sea instead of landing on Helgoland, depending on wind conditions. Results: Both wind and relative humidity the night before arrival were correlated with arrival fuel load. After nights with strong headwinds, birds caught the following day were mostly lean, most of which would not have managed to cross the sea if they had not stopped on Helgoland. On the other hand, fat birds that could have successfully travelled on were caught mainly after nights with high relative humidity (≥ 80%). Furthermore, the rate of presumably successful flights was lower due to wind: although only 9% of all blackbirds captured on Helgoland had insufficient fuel loads to allow safe onward migration in still air, real wind conditions would have prevented 30% of birds from successfully crossing the sea during autumn and 21% during spring migration. Conclusions: We were able to decipher how physiological condition, wind and relative humidity force blackbirds to stop on a remote island. Adverse winds tend to affect lean birds with low energy resources, while poor visibility affects all birds, regardless of whether the arrival fuel load was sufficient for onward flight. Our findings will help to understand different migratory strategies and explain further questions like migration timing.

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Electron Microscopy in the Study of Natural Phytoplankton Assemblages

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100119831 ◽

1985 ◽

Vol 43 ◽

pp. 620-623

Author(s):

Linda Sicko-Goad

Keyword(s):

Electron Microscopy ◽

Aquatic Environment ◽

Size Range ◽

Physical Parameters ◽

Specific Information ◽

Phytoplankton Assemblages ◽

Phytoplankton Productivity ◽

Ecosystem Effects ◽

Time Of Year ◽

Species Specific

Although the use of electron microscopy and its varied methodologies is not usually associated with ecological studies, the types of species specific information that can be generated by these techniques are often quite useful in predicting long-term ecosystem effects. The utility of these techniques is especially apparent when one considers both the size range of particles found in the aquatic environment and the complexity of the phytoplankton assemblages.The size range and character of organisms found in the aquatic environment are dependent upon a variety of physical parameters that include sampling depth, location, and time of year. In the winter months, all the Laurentian Great Lakes are uniformly mixed and homothermous in the range of 1.1 to 1.7°C. During this time phytoplankton productivity is quite low.

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